i gotchu blud
English Transpositions

english defense, its a lightsquared-based opening that is reliable and fun, you get good counterplay with Bb4 and f5

It all depends from what both sides want to propose.
Generally English players like to keep it in English territory which is why I recommend you play your d4 reply and poise him the question to transpose or not?
If he transposes, he has to understand some d4 theory or learn to navigate into your preparation.
The KID or Grunfeld and Caro-Kann games are the most challenging defences against the English from my experience.

Having recently entered a ratings bracket where I’m regularly facing 1900+ players, I’m beginning to see many more English games, and my prep is lacking. I’ve tried the Reversed Sicilian, Anglo-Scandinavian, and Hedgehog, and Ultra-Symmetrical. However, I’ve recently discovered that Black can just… play a KID/Grunfeld and White’s best and most common option is to play into it, is that correct?
white can play agianst these with the botvinnik system

Hi, though obviously I'm much lower rated than you, I almost always play the English as white, which is why I hope I can help.
First of all let's go over the options (though likely you know them all): Reversed Sicilian (e5), Anglo-Scandi (d5), Symmetrical (c5), Great Snake (g6), English Defense (b6), Agincourt (e6), Caro-Kann System (c6), Anglo-Indian (Nf6), and Anglo-Dutch (f5). Other than these options, I would classify the rest as completely unsound (though I would say the same about the Anglo-Scandi...)
Group #1: Agincourt and Caro-Kann System Defenses:
Both the Agincourt and Caro are very solid and reliable defenses into the English Opening. However, the downside of both openings, is that White has the option of transposing into a Queen's Gambit with d4, so you will need to study the QGD or Slav theory. If this isn't an issue, either of these two are great options and give black good counter-attacking opportunity.
Group #2: English and Great Snake Defenses
The English and Great Snake Defenses are similar in that they aim to allow white to take a broader center, and prepare to strike it using their fianchettoed bishops. However, the Great Snake is a much better option, as it allows for a quick short-castle, and fianchettoes further from White's pawns. The English Defense can get very tricky for Black to play well when White starts building towards e4.
Group #3: Reversed Sicilian, and Anglo-Indian Defenses
Both the Reversed Sicilian and Anglo-Indian Defenses are a great way to fight 1. c4. Both are played at the top level, and are very solid if played correctly. Reversed Sicilian often allows for 2 main attacking plans for white e3 to push d4 with support, and/or g3 to fianchetto the Light-Squared Bishop. Anglo-Indian is also a top-tier way to fight against the English. However, as you mentioned, move orders can be tricky, and white can push for d4 whenever they want, which is why understanding theory and ideas for this opening is key. Anglo-Indian and Reversed Sicilians often transpose into one another, since they both involve Nf6, and e5 will often come naturally in a given English Position.
Group #4: Anglo-Dutch Defense
Though the Anglo-Dutch is a risky, it is a great fighting way to attack the English, creating double-edged positions, and creating good attacking potential. If the Anglo-Dutch is played, black should aim to place his Knight on f3, his bishop to an available active square. This is my personal choice for an exciting and fresh way to counter the English.
Group #5:
I consider the Anglo-Scandi to be an unsound way to play against the English, due to a delay of development, and it's slow nature in creating attacking chances. In my opinion, it creates a relatively easy game for White to play, and poses him no real threat until much later in the game.
As you mentioned, in almost all of these openings, White can choose to play d4 at any time. If the opening you choose is this case, you must study theory if White chooses to go down this route. However, this is not always the case, so you must be prepared either way. Feel free to contact if you have any questions.
Hope I can help,
Ostrich

Having recently entered a ratings bracket where I’m regularly facing 1900+ players, I’m beginning to see many more English games, and my prep is lacking. I’ve tried the Reversed Sicilian, Anglo-Scandinavian, and Hedgehog, and Ultra-Symmetrical. However, I’ve recently discovered that Black can just… play a KID/Grunfeld and White’s best and most common option is to play into it, is that correct?
white can play agianst these with the botvinnik system
The knight goes to e2 in the Botvinnik System.

Hi, though obviously I'm much lower rated than you, I almost always play the English as white, which is why I hope I can help.
First of all let's go over the options (though likely you know them all): Reversed Sicilian (e5), Anglo-Scandi (d5), Symmetrical (c5), Great Snake (g6), English Defense (b6), Agincourt (e6), Caro-Kann System (c6), Anglo-Indian (Nf6), and Anglo-Dutch (f5). Other than these options, I would classify the rest as completely unsound (though I would say the same about the Anglo-Scandi...)
Group #1: Agincourt and Caro-Kann System Defenses:
Both the Agincourt and Caro are very solid and reliable defenses into the English Opening. However, the downside of both openings, is that White has the option of transposing into a Queen's Gambit with d4, so you will need to study the QGD or Slav theory. If this isn't an issue, either of these two are great options and give black good counter-attacking opportunity.
Group #2: English and Great Snake Defenses
The English and Great Snake Defenses are similar in that they aim to allow white to take a broader center, and prepare to strike it using their fianchettoed bishops. However, the Great Snake is a much better option, as it allows for a quick short-castle, and fianchettoes further from White's pawns. The English Defense can get very tricky for Black to play well when White starts building towards e4.
Group #3: Reversed Sicilian, and Anglo-Indian Defenses
Both the Reversed Sicilian and Anglo-Indian Defenses are a great way to fight 1. c4. Both are played at the top level, and are very solid if played correctly. Reversed Sicilian often allows for 2 main attacking plans for white e3 to push d4 with support, and/or g3 to fianchetto the Light-Squared Bishop. Anglo-Indian is also a top-tier way to fight against the English. However, as you mentioned, move orders can be tricky, and white can push for d4 whenever they want, which is why understanding theory and ideas for this opening is key. Anglo-Indian and Reversed Sicilians often transpose into one another, since they both involve Nf6, and e5 will often come naturally in a given English Position.
Group #4: Anglo-Dutch Defense
Though the Anglo-Dutch is a risky, it is a great fighting way to attack the English, creating double-edged positions, and creating good attacking potential. If the Anglo-Dutch is played, black should aim to place his Knight on f3, his bishop to an available active square. This is my personal choice for an exciting and fresh way to counter the English.
Group #5:
I consider the Anglo-Scandi to be an unsound way to play against the English, due to a delay of development, and it's slow nature in creating attacking chances. In my opinion, it creates a relatively easy game for White to play, and poses him no real threat until much later in the game.
As you mentioned, in almost all of these openings, White can choose to play d4 at any time. If the opening you choose is this case, you must study theory if White chooses to go down this route. However, this is not always the case, so you must be prepared either way. Feel free to contact if you have any questions.
Hope I can help,
Ostrich
A 1400 with knowledge and experience will always be more helpful than an arrogant 1900 who doesn’t know what they’re talking about, I appreciate the advice. Personally I find that the Anglo-Scandinavian can work, but similar to the Alekhine’s Defense, it’s far too much effort for too little reward.
Having recently entered a ratings bracket where I’m regularly facing 1900+ players, I’m beginning to see many more English games, and my prep is lacking. I’ve tried the Reversed Sicilian, Anglo-Scandinavian, and Hedgehog, and Ultra-Symmetrical. However, I’ve recently discovered that Black can just… play a KID/Grunfeld and White’s best and most common option is to play into it, is that correct?