Bit of a tricky one - I am really interested in the fast cars, but I struggle more with driving/racing them. Sometimes I can't keep up with the car, or have trouble managing the power and spin if I sneeze at the wrong time. Sure that's on me to "get better" and to be fair I don't spend a lot of time with F1 types. Also if it's something like an F1 car there's more things to manage like DRS, KERS, fuel maps, etc. which gets compounded by the higher speeds. They're awesome, but kind of a lot of "work".
I race completely offline, and spend most of my time in RF2. My favorite cars are probably GTE and GT3, they're still very "cool" and fast but not insanely so - BUT I'd say the best racing I've had vs AI (at least in RF2) has been with the USF2000 and Tatuus F4. Quick enough to be fun but not really a concern about the car getting away from me (it still happens but usually only if I really mess up), I'm more comfortable to push harder in them and just seem to have mostly really good races with them (once the AI settings for a given track get sorted out). They're also simpler with less variables to manage throughout a race or even lap by lap, just anti-roll bars and maybe brake bias I think - which I usually don't anyway. So, I just drive and concentrate on my lines and references.
I used to do a little bit of kart racing, mostly "arrive-and-drive" endurance events where the race organizer brought all the karts and equipment and you just pay your fee, show up with your team, and race (a few of them were run by Johan Schwartz, who does pro touring car racing). The karts only had a top speed of around 50 - 60 mph I think - but it didn't matter, on a kart track racing wheel to wheel with people it felt like 150, it was a total blast.
The funny thing too is in reality, I'd bet if most of us who don't race in real life ever got the chance to drive an F4 car it would be the fastest thing we'd ever experienced. Unless you've had the chance to wring out something like a modern(ish) Corvette, Porsche, or something more exotic on a track big enough run up past 3rd gear (or on public roads going way faster than is wise). But, on a road course without a straight long enough for big power to knock down lap time I bet an F4 car would lap faster than most road spec "super cars".