the rx-8 is a coupe. end of.
there isnt really one standard definition of what a coupe is, its generally a 2 door car but can have 4, usually has frameless doors, but so do some saloons, often doesnt have a B piller, and has either 2 or2+2seater layout, but most importantly the modern definition has to have an interior capacity below a certain amount which technically means a ferrari 612 is a 2 door saloon car
on stagecoaches where the term comes from they were 4 seater coaches that had the front rear facing seats removed to create a smaller 2 seater coach.
the definition changes over time, convertables used to be called coupes as well. which is where drophead coupe comes from for RR convertables.
