We'll have to wait on the IQ...but people are reporting...these are the same lens design. Just one with an EF mount and another with the RF mount.

See Bryan's take here.

So, you do not need to worry about an adapter...0.5 more stops.

As for AF performance, especially with extenders, maybe there is a benefit, but we'll have to see. But not a run out with credit card waving type of announcement, IMO.

Granted, someday, when my kit is all RF, I'll probably own the 100 f/2.8. That does look like a great lens.