Which should I play- Semi-Slav Meran, or Triangle Stonewall?

You have left out the really crucial bit about how to deal with the catalan.

Curious dilemma, but 4...Nf6 is clearly better than 4...f5.

Indeed. Mainline, established theory is always the best at any level imo. The trick is, getting your experience, skill set, chess philosophy on par to realize for yourself which is ultimately the best (respectable & solid) for you; first and foremost-not the lines. Best wishes✌🏽

How bout annotate it please and how bout the noteboom?

Indeed. Best wishes.

The most reputable openings at top level typically imply truckloads of theory and countless sidelines, which is the case for the Meran, the Sicilian Sveshnikov, the Catalan and many other frequent guests in GM games. For such openings, 15-move-long home preparation is no more than an appetizer for competitive players. There will be a lot of work if you want a thorough study on one of them!

That certainly doesn’t mean we amateurs who don’t have the time to follow theory trends can’t enjoy these openings, though. The amateur player might love the Sicilian Dragon for its tactics, the Meran for its dynamic play, the London System for the beauty of maneuvering, or the King’s Indian simply because (s)he likes to have his king’s bishop fianchettoed. Each opening has a few charming characteristics, which has nothing to do with whether the opening is sound.

Soundness is measured, and should be applied, at a level where everyone studies opening theory extensively. Unless your goal is to reach that level, soundness shouldn’t be an important factor when choosing what to play. It’s much better to go through a dozen GM games of a particular opening and decide whether it fits your playstyle.

There is a vast space between the most respectable openings and the most suicidal gambits. The majority belongs to this zone of “playable” openings and, as the name suggests, they are good enough to be subjected to serious study. Experience has proven that the most practical choice is the opening you’re most familiar with. So basically you choose whatever “playable” or “respectable” opening, invest some serious time studying it and it will — don’t worry — become the best practical choice for you, be it the Meran, the Stonewall or something else.

Well, Catalan is Leela's favourite opening. Dealing with Catalan will requires significant positional understanding.

Leela see Catalan as 54.6 % scores according to her training experience. 

For OP question, all these opening you mentioned above are sound opening, and playable at any level. The choice depends on your home preparation and your familiar with positions!

Same analysis, but GUI showing winning chances of many variations.

Same analysis but showing all variations. (Note, leela see your winning chance drops to 1% if you drop a piece like 3. Bh6??

Thank you for your help. I would rather play black in that variation than in the Marshall gambit. I am not a computer, so I am not a fan of playing the Botvinnik variation or anti-moscow gambits either. Last I checked, Cambridge Springs variation has very few up-to-date opening resources on it, and I am under the impression that white has an edge anyways if he knows his stuff. Also, the winawer counter-gambit scores very good for white, last I checked.

But yeah, I am not willing to play the black side of the Marshall gambit under almost any circumstances.

Scherbakov gives lines like this in his triangle book. 

Yes suprisingly in semi-slav lines you take on c4, with intention of holding pawn with b5. At least the OP in https://www.chess.com/forum/view/chess-openings/semi-slav-thinking-to-catalan-position-now-what-change-opening-1 thinks there is something untypical that needs to be explained about d5xc4.

#7:  "Unless your goal is to reach that level, soundness shouldn’t be an important factor when choosing what to play. It’s much better to go through a dozen GM games of a particular opening and decide whether it fits your playstyle."

I never thought about that.  This makes sense.

I don't have time at this moment to compile all the things that led me to these conclusions, only for you to tell me that I am stupid or something. But here is one source of information that helped me come to a conclusion about the Cambridge Springs.

This is not a good advertisement for the Cambridge Springs variation.

Excuse me? If people like you are going to claim that I am being "disingenuous" for quoting pfren's comments on the variation, what is the point of arguing on the internet at all? There is nothing dishonest in what I am saying, but that doesn't stop some random guy on the internet from throwing around accusations.

Alright sir, let's take a look at one issue at a time.

You say, "I have no idea how you could come to such conclusions. Take for example the Camrbidge Springs: Almost all strong players do not bother entering the main lines, and play either 6.cxd5 (which results in a regular Exchange variation) or 6.a3."

And then I show you a reason why I might hold my conclusions about the Cambridge Springs. In fact, I show that you once held such conclusions yourself. I did not even quote this more negative advertisement for the Cambridge Springs, because I thought the first quote was perfectly adequate to demonstrate how I could come to these conclusions. But let's take a look at another comment.

So, do we agree that I have successfully shown how I could have come to such a ridiculous conclusion as "white has an edge" in the Cambridge Springs variation? After all, you held to such a conclusion yourself, and you even seem to hold it today, since you still do not want to play the black side.

If you agree, do you also admit that it was incorrect/wrong of you to act as if it is a ridiculous conclusion to make? Do you now have some idea, as opposed to "no idea," as to how I could have come to this conclusion?

________________________________________________________________________________________________________

Let's assume you concede all of the above, and let's move to the next issue. Now you accuse me of not scrolling down to post 15 in that thread, as though you renounce your previous statements in that post. In fact, I had read that comment. 

Now, why didn't I quote this comment earlier? Because it does not, in fact, contradict anything you said earlier. "The position is probably holdable, but not really pleasant to play, and certainly not very ambitious." This game does nothing to contradict that. It does not even contradict your much more negative expression of dislike towards the black side, where you say, "I will certainly consider playing it, when the other openings will be banned." Black is able to hold the position in this game, but this hardly demonstrates black holding in a pleasant way.

In fact, in your recent post, you show another game in which black holds, and you still admit that you do not like black's position! That's not really a good advertisement either.

So, now let's take a look at this remark. 

Do you admit that you were wrong when you accused me of not scrolling down to read this post?

Do you admit it was wrong to imply that this post renounced any of your previous comments on that post, when that comment did not do anything of the sort?

And do you admit that it was wrong, given all of the above, to respond with such a snide remark as "You are cool!   "

Or do you refuse to admit to any of this?

It seems that despite pfren being a senior citizen, he never matured to the point of ever being able to admit that he was wrong.

I rest my case.