Without pictures of the RRS plate available yet, question is if the plate does extend below the battery door / grip area. If so, the additional height obtained this way will improve the grip on the camera.
Exactly, I had this type of plate on all three of my Sony's and it really improves the handling, really don't want to go back 5 years in time and use a regular generic shaped plates.
It might be needed however to remove the plate in order to exchange the battery. The RRS plate for the Sony A7iii/A7riii/A9 is like this, with the option of moving the (removable) battery door to the plate.
Also don't like this for two reasons; I want to keep the camera sealed at all times when in the field as I do shoot in the rain and also want to keep the battery door out of the dirt when placing it on the ground.
I've used cheap eBay brackets for the Sony's which worked pretty well as a grip extender but had too much flex for serious tripod use, they were OK for the few times a year I actually used a tripod but for the Z6 I want to have a solid plate with a grip extender.
Maybe my eyes are fooling me but based on early reports of the Smallrig on DPReview it seems that their design also has too much flex when heavier lenses are mounted, see the attached image.