I got rejected for speedrunning optifine 1.17.1. Is there any other fps boosting clients that are aloud ?

sodium

maybe read the rules

Optifine has never been particularly liked by speedrunners because it makes very small changes to things like how mobs spawn, so isn't technically "the same as vanilla apart from performance", as speedrunning mods are required to be. Performance improving mods are necessary for too many people though, and most versions don't have a better alternative, so these versions allow optifine until something better is eventually found/developed. For 1.15+, sodium is available which does the job much better, so optifine is banned for these versions.

read this https://www.minecraftspeedrunning.com/public-resources/mods