How much storage space should I leave free in my SSD?

I have an ssd of 4tb I use for my pc games only and it's close to filling up ( I like to keep all my games installed rather than re-downloading them later - don't judge me). Currently have 200gb remaining. I've read that it's recommended to leave at least 10% so it won't slow down the ssd, but if that's true, 10 percent of 4tb would be around 400gb and that seems like a lot. I was thinking about leaving 100-150gb and save any future games on another 4tb ssd I plan on buying later. Any experts have any suggestions or recommendations on what I should do? It's mainly to avoid slowing down my ssd. As I stated before, they're only for games primarily. All my files/documents and additional programs are stored on another drive.