I think it depends on what you want to make a clone for.
TGM rules are more elegant and much more challenging for single-player tetris, but on the other hand multiplayer and especially 1v1 has far greater variety and dynamism with a looser rotation system. The stricter the rules, the more it becomes spamming tetrises against each other until someone misdrops. You have to construct a ruleset where a player who is 0.1pps faster doesn't just autowin.
TGM rules are more elegant and much more challenging for single-player tetris, but on the other hand multiplayer and especially 1v1 has far greater variety and dynamism with a looser rotation system. The stricter the rules, the more it becomes spamming tetrises against each other until someone misdrops. You have to construct a ruleset where a player who is 0.1pps faster doesn't just autowin.