It's mulitple mods to replace. But since you need perfomance, all you literally need is optifine and patcher. Thats the only reason why you're getting good FPS with these clients, lmfao.
https://alternatives.microcontrollers.dev/1.8.9/home/ you can find more here if you want, I can also give you my personal mods list.
that is because they use optifine and patcher. Those two mods are readily avaliable (
https://optifine.net/downloads &
https://sk1er.club/mods/patcher). That is all you need if you only use clients for FPS boosting.
All these clients use these two mods to "boost" fps - they are all a gimmick to sell user data from children who dont know any better lmfao