Most of what you read about the methylation protocol tends to be on the pseudoscientific side, or just pure speculation, so take it all with a pinch of salt.
The methylation protocol was very popular to investigate methylation as an ME/CFS treatment around 10 years ago, after Rich Van Konynenburg, a retired physicist, had a theory that ME/CFS may be due to insufficient methylation (I think he based this on Amy Yasko's work).
In spite of the often pseudoscientific complexities posted about methylation on this forum, it's actually a simple protocol to try: you just take some B12, active folate (like methylfolate), and some supportive supplements like lecithin. There is a
section in my roadmap which provides further details. The last version of this protocol before Rich died was posted
here.
Lots of people tried it, but it never panned out as the explanation of ME/CFS. Nevertheless, it still may be worth trying, as it might result in some benefits.
Myself, I find when I take doses of methylfolate (aka L-5-MTHF) higher than 100 mcg, after several days to a week, I get into a state of overmethylation, which is characterized by an agitated overstimulation of the brain, which is somewhat unpleasant (you can counter this overstimulation with niacinamide 500 mg or more).
However, I also find that methylfolate significantly improves my brain fog, and ability to do productive work, once its effects kick in, after about a week. But generally I find the overmethylation state unpleasant; you cannot relax at all with this 24 hour overstimulation feeling.