king's Indian or queens indian
Best opening against d4.

There is no "Best". Merely a finite number of sound openings, namely 8 of them. You have to put in some serious studying at a board, not just playing blitz games.
Those 8 options are, in no particular order:
1) Queens Gambit Accepted
2) Queens Gambit Declined
3) Slav Defense
4) Semi-Slav Defense
5) Nimzo-Indian Defense (Paired with QID or QGD)
6) Grunfeld Defense
7) Kings Indian Defense
8) e6-Dutch Defenses (Classical and Stonewall)
Everything else is either dubious (Chigorin Defense, Leningrad Dutch, Modern Defense) or outright bad (Englund Gambit, Albin-Countergambit).

I'd recommend a fighting opening over a positional / theoretical one. That'll force your opponent to play precisely early on, something most players won't do.
Here are my typical recommendations
- Slav
- Tarrasch
- QGA
- Benko (or Blumenfeld)
- English Defense
- Triangle Slav
- Possibly the Nimzo Indian combined with the Vienna, Blumenfeld, or Bogo
In general 1... Nf6 handles the junk better than 1... d5, but both are perfectly viable.

Those who play 1.d4 either go into a system opening, think London, Colle, Zukertort; or they want to play a mainline. So all you have to do is look at what you want to get out of an opening against the system players and then choose a good line against non system players. I tend to play the Dutch as it works well against system players and you get main line Dutch for non system players. But other things to consider are stonewall or semi-slav openings. Maybe play 1.d4 e6 and see what the other player does so you can avoid Staunton gambit, or go into a French if 2.e4.

Those who play 1.d4 either go into a system opening, think London, Colle, Zukertort; or they want to play a mainline. So all you have to do is look at what you want to get out of an opening against the system players and then choose a good line against non system players. I tend to play the Dutch as it works well against system players and you get main line Dutch for non system players. But other things to consider are stonewall or semi-slav openings. Maybe play 1.d4 e6 and see what the other player does so you can avoid Staunton gambit, or go into a French if 2.e4.
Ok. Do u know the best ways to study these openings? Specific YouTubers are courses, etc?
I don't do well against d4 generally so can someone recommend some for me