Many substances are very important in theory but I don't tolerate them well, like NAC, I don't tolerate that either. The thing I had most success with until now are certain unactivated, single b vitamins (and minerals).
I think some processes are very important, like glutathione synthesis, the
energy metabolism (pyruvate dehdrogenase, fatty acid oxidation), methylation, and I try to find cofactors for these processes that at the same time have a calming effect and don't overly activate stress secretion.
Vitamin B2/riboflavin supports glutathione and is a cofactor for the MTHFR enzyme, B3/niacin helps glutathione synthesis and can reduce adrenaline levels. It can decrease methylation though (this can raise histamine).
I have better experience with sublingual hydroxcobalamin than other b12 forms, I think it's better not to take activated forms because those might 'do too much' and deplete minerals more.
I started taking vitamin B5/ Calcium Pantothenate again. It is very important for the energy metabolism because it forms Coenzyme A/ CoA-SH which becomes a part of acetyl-CoA.
Sometimes, I also take magnesium and vitamin B1, but I don't tolerate vitamin B1 well mostly..
So I have this very minimalistic approach at the moment, because I feel almost everything on top of that depletes those for me relevant cofactors again. I can just recommend what I'm doing at the moment, B2,B3, hydroxoB12 (magnesium), and now trying B5. I don't really have other ideas on supplements and don't tolerate most other supplements
There also seem to be individual differences on how well you tolerate b vitamins, which I think makes sense. For example, if you don't have any MTHFR mutations but always high B12 requirement, you might not tolerate B2 that well. And I take rather low doses of everything. So I would consider carefully trying some of these vitamins alone and see how you tolerate them.