I’m not sure if this is how proton notifies you, but it could also be that someone else (the other address you’re seeing) put you in as their recovery mail. they haven’t logged in in a while, and now get notified that their account might get deleted due to lack of activity. They might have just mistyped the intended recovery email or randomly put in yours. Either way, nothing you need to do.
I don’t think there are benchmarks specifically for hosting minecraft, but I guess general purpose benchmarks can give you a pretty good estimate. You could spin up a server on your homelab and just stress-test it a bit to see if it is noticeably worse than the other instance. You’ll have to weigh the saved costs against the (likely) worse performance. on a side note: there are great options to make minecraft playable on servers with less CPU power, like using i.e. a paper server, performance mods, or lowering the renderdistance and ‘faking’ more renderdistance with client-side mods like bobby or distant horizons.