I doubt if there would be much difference.
Games and game levels load faster from an SSD, that's for sure. Framerates are going to be unchanged. The actual spec of the SSD is not going to make much of a difference on how long the game/levels will take to load (unless it's a really old SSD - even then it's not going to be night/day difference).
Personally, I'd keep the game install on the same SSD as the OS, but I doubt having the games installed on a secondary SSD will have much impact.
The main thing is - game on SSD will load faster than game on HDD.