Hi,
I have a 73cm (29'') wide tandem folder and I prefer my 222cm GP to my 240cm EP.
I can make a quicker short sprint with my EP, otherwise GP is as efficient as the EP or better - and I get much less tired. I have never had carpal tunnel/elbow/wrist/shoulder or back problems, but I
still always use the GP when possible - that is, when the front paddler isn't using it.
I am looking for (or I'll try to build) another GP of minimum 240cm - the opinions differ a lot on whether that length is better or if one should stick with a shorter GP and use sliding strokes, see below.
The GP does occasionally hit the side while paddling (so does the EP).
Most of the time I reposition my hands about 10cm for each GP stroke - that is a (semi-)sliding stroke. It is automatic and doesn't require any attention from me. If I want a slower, heavier "gear" I increase those 10 cm to, say 20 or 30 (higher values great for turning) - it's a very easy and intuitive feeling. My pushing hand is never higher than my chin, I almost never use my thumbs, and I only use the four other fingers for pulling, I push with a flat hand. I can (briefly) exceed 6 knots alone in my double folder with either GP or EP.
I am 185 cm tall with arm span of 200cm, but my wife is 165 with normal arm span and she also prefers the GP. I don't know if my long-ish arms are an asset wrt. GP paddling.
This month I'll receive my late grandfather's SOF from 1928 - can't wait

and then I'll see if the GP works even better with a narrow kayak.
It's a really good idea to try one or more GP's before buying, if possible. That said, I'm sure it's easy to get rid of second hand - and most likely you'll want to keep it, at least as a spare or for variation.
If you are just starting out, the GP will be at least as easy as the EP to get used to. If you are a seasoned EP paddler, you might need a few weeks or months to readjust.