There isn’t much of anything that’s helpful.
100% trial and error - also leaving Alpha engines like 5 alone is a great idea, both for sanity and because of the fact epic does not pay you or me to be their tester on trash they release knowing it won’t work…
There’s pretty much no one that does animations and character setup right in any form or shape.
Epic’s hire Laurent is the only one showcasing and explaining basic things during hour long (and longer) talks. Out of which you have to learn, undesrstand, re-create, test, and asjust.
There’s a few folks that do decent shader tutorials: ben cloward, I believe is the last one I know of that epic didn’t buy/hire.
Of the epic employess you’ll find helpful stuff on shaderbits.io, and some dated videos from when chris murphy and De Jong were not with epic.
Also any of their official epic talks are often worth the time it takes to watch them at x2 speed.
Theres pretty much no one that does landacape systems correctly - and be aware that anything you watch on the subject is very likely trash if it deals at all with stuff inside the engine.
There’s some decent tutorials on using SFX Houdiny for this. Use/learn those.
On optimization, you’ll find a lot of BS and opinions by just about anyone. But the ones to listen to are Intel. They usually release papers on optimizing unreal, kind of like GPU Gems used to be.
Everything else about the engine is either stuff you should probably not utilize, or stuff you can quickly pick up which works somewhat like you’d expect. It depends on what it is, and on why you are attempting to use it.
On most projects we consult for, the developers just have no idea what so ever of what something should look or function like in the first place, so they attempt to levarage pre-made stuff to save time and then are faced with having to replace the whole system later on…
Top amongst these is the water system, second is the landscape, third is badly created characters…
As a general rule of thumb, assume that any youtube video you watch on any subject is an OPINION, and not an “how to”.
There likely is a better / best practice way to re-do whatever the video explains.
If you learn the concept expressed, and you are able to re-apply it into other situations, then you got something which was worth learning out of it…
Edit:
I forgot one guy who’s important to advanced shader techniques when it comes to learning stuff you didnt yet even think of - who I also believe isn’t an epic employee.
Tharlevfx
Hes got a youtube channel and shares some good stuff for UV manipulation / avoiding tyling and so forth.