Honestly, would you buy ...

RP, hands down.

RP pros:

Cheaper, lighter, better AF, better ISO, better video AF (by a lot), RF and EF glass access.

Z5 pros:

Joystick, dual slots, higher quality EVF, IBIS

.

The joystick is not going to save the lackluster AF of the Z series, and the AF of the Z5 will be even more poor (vs the Z6/Z7) since it's based of the A7 II sensor meshed with Nikon firmware!

Likewise, comparing the PDAF of the A7 II sensor vs EOS RP DPAF? You've got to be joking.

The Z5 looks good on paper, but man when you look at just the AF alone of the Z5, it's like the A7 II, except even dumber as it doesn't have Sony's AF firmware. Ugh. Bad backend (slow old sensor) + bad front end (class-trailing Nikon mirrorless AF firmware) = AF disaster ala EOS M (original).

IBIS is nice, but, the Z format is lacking glass which to use IBIS with?

Nikon needs to come down in price, fast, on that Z5, unless, your purpose is landscapes. But then, shoot a A7 II and post process it to death to make up for the bad colors.

The RP is a no brainer vs the Z5. Like I wouldn't blink. If you could hold both in BestBuy, it'd be obvious to anyone trying both...

Think of it this way...

No offense to the EOS M (original), but it's autofocus was it's undoing. Think along those lines and we're on the same wavelength.

Like the original EOS M, it saw firesales shortly after it's launch where an EOS M + 22mm could be had for $249. And for static objects, it was killer for price and size. The Z5, if it comes down in price, could be similar in terms of it's fate I predict.