NekuroMC

yes

nice thank you i dont know where i would use this but its good to know

I figured out how to make the model change with potion effects.

In a pre_parallel, change the scale of the part of the model you want to be affected by the potion effect to "ysm.effect_level('minecraft:[effect]')".
For example, if you want the character to have bunny ears when the speed buff is active, click the ear group and in pre_parallel, change the scale to "ysm.effect_level('minecraft:speed')".

Additionally if you want a part of the model to be removed by a potion effect, set it's scale in pre-parallel to "1-ysm.effect_level('minecraft:[effect]')".

Not sure about the hair thing, I found this video on bilibili which looks to do with hair rotation, but it's in Chinese. www.bilibili.com/video/BV1DF4m1K75J/