Oh boy penhold grip & RPB. Here we go.
I grew up being taught TPB by my brother. I posted this video years ago talking about more curled finger approach. Interestingly enough, I like this curled fingers approach if you twiddle. I did that for a long time playing inverted on one side LP on the other. With fingers more extended, it's nearly impossible to twiddle quickly IMO.
That being said, I've since adopted a more modern penhold style of playing duel inverted and playing much more RPB as compared to TPB. With this change i like the more traditional grip that I first talk about in the video. I feel it gives me more power on the forehand to have the fingers more behind the face of my blade.
As for RPB, I probably should get video but for me when I was a kid (started playing shakehand) my backhand was the strongest part of my game. I honestly don't feel like it's much different. I have a pretty good RPB and I've never felt like I was going to hurt my wrist or anything. Now my fingers? lol. That's a different story. There's so much torque & pressure on those, I get blisters all the time. I have these finger sleevess that are simply awesome if you encounter the same thing. But I digress.
To me if you can throw a Frisbee, you can do RPB. On blocks i don't use hardly any wrist. On counter drives & loops, in addition to arm, torso, etc, I do use a fair amount of wrist. It should be relaxed.
One difference from what I've seen between penhold to shakehand is that say on shots to your elbow, my shakehand partner can lean over and backhand block or counter those shots in. For me, that's really awkward to try with RPB. With penhold, I'm better off TPBing those blocks or moving quicker to play the standard forehand.
Just my 2 cents.