i have a question. what is the btt best theoretical time?

Depends on what you mean by BTT, because it can have various meanings.

SMB1 doesn't have BTT, it has a Human TAS instead, and that is 4:54.6xx if I recall correctly. However, that time is almost a framerule slower than Niftski's Sum Of Best for Any%, which is a 4:54.3xx. So, depends on which one of these you consider the Best Theoretical Time.

Well, the no l+r tas could also be considered btt since it technically is possible on a nes controller. Yes 1 frame in 8-4 is considered impossible, but so was flagpole glitch at one point for the same reason; to complex of inputs for a human. And look we’re we are now