It's not the purpose of TRIM to give a speed boost. The purpose of TRIM is to maintain the drive's Read/Write performance.
Modern SSDs don't rely only on TRIM to maintain drive performance; they also use Garbage Collection to maintain performance. So no, TRIM is not compulsory.
Yes, most SSDs will slow down when they are more than 90 percent full.
,how bout ssd in raid 0?? will they be able to activate trim?? cause i plan to have them in raid 0 for speed boost and also wont slow down even when almost full, also does 2 of them in raid 0 gives a ton of boost?