Yes, the G5 patch is not only for JIT.
This Beta 1 doesn't have this G5 support at the moment. But we will include this in later releases (most likely Beta 2), so you can profit from more speed.
Also in Beta 2 there will be video overlay for MorphOS E-UAE.

For your Config problems:
The cachsize must be between 0 and 16384. Note that JIT only will be active, if set. 0 and not supported values will turn the JIT off, resulting in a black JIT LED field.
The switch "enable_jit" is not neccessary afaik as JIT will be activated when setting cachesize and a CPU which can use caches.
amiga.use_overlay will be used in the next Beta.