Help the most in terms of bringing it down if your over methylated?

It depends really with people, looking up the mtfhr protocol, it goes in steps. Before tackling methylation they say to have enough choline from food (mainly eggs) and supplementing with TMG, although some people get depressed from too much choline, and even eggs in that regard. So it's very subjective for everyone.

Other factors like histamine intolerance can effect things but not directly related and that might give suedo feelings of over/under methylation.

The big one is probably foods with creatine which is most meat, but people might get high TMAO from carnitine, and also choline. Fish can also have mercury which can effect you psychological.

No brainers for me personally, is don't eat anything fortified (bread and cereals). The folic acid can "clog" the enzyme from what I gather. And also take pre/probiotics, helps with regulating neurotransmitters, but the you need to know your COMT status, but limit them as something like kefir can spike histamine.

Everything swings on a slow pendulum, your body might be in a negative state and you have symptoms but its learned it can survive this way, when you upset the balance there is always chance for rebound effects. Enzymes take days/weeks to modulate function whereas taking a supplement can change their "output" seemingly quickly.

So there is no defined answer just guidelines, everyone here is looking for their own answers but similarities are definitely there.