Which emulator is used in this run: https://www.speedrun.com/tetrisgb/run/y6p525jm ?

Which mobile emulators have correct speed and handle lag properly?

It's a good question, and I don't have the answer. I have accepted these runs after studying them to the best of my ability. I cannot prove or disprove whether they are running at the same exact speed, but I have done a few crude tests timing the line clear animation against my own, and they seem to line up.

As far as lag goes, to my knowledge this game has none, but I could be wrong. I am doing my best ¯_(ツ)_/¯

I think the lag is probably generated by the mobile itself. Anyway, the speedrun is done with the emulator My OldBoy!