Reviews of various Canon RF cameras:
So what would Thom get? The RP is a bare bones, entry camera. You buy it because of price. The R is an oddball camera that doesn't really hold up against current competition, I'd buy it only on deep sale.
The R3 is certainly a good choice for those looking for a fast frame rate flagship mirrorless camera akin to the 1DX, but I don't regard the R3 as a more general camera due to the pixel count, among other things.
The most well-rounded of the full frame cameras is probably the R6, which brings the best of Canon's DSLR world into the mirrorless realm pretty much intact, while adding some mirrorless-only aspects. The R5 is the top end if you need the pixels, but the R6 is the camera most should be looking at.
Finally, with RF-S now a thing, the R10 (basically a mirrorless Kiss/Rebel) and R7 (somewhere between the 90D and 7D II DSLRs) are well worth looking at. The R7, in particular, is a solid camera capable of most everything most people would need.