I have a Model 3 and I ride XL frames. I think my biggest one’s a 63cm. This also means I have the drivers seat all the way back.
All my bike’s fit with only taking the front wheel off…BUT, I have to lower the seat because that top of seat to bottom of rear wheel/crank dimension doesn’t slide in sideways between the rear wheel wells in the trunk. This makes a mtn bike easier because you simply lower the dropper post and take the front wheel off. With my road/gravel bikes I have to get out the allen wrenches and drop the seat and then make sure I set the seat back to the right height. Not a deal breaker, but kind of an annoying added step. Obviously if you take both wheels off it fits easily without dropping the seat. With QR skewers that’s almost easier than messing with the seat height.
I’ve looked at getting a roof rack but they’re uglyAF on the car, it kills the aesthetic, and you lose mpg (or kwh/m, or however it’s measured). I’ve looked at the seasucker things, but they’re expensive and there’s anecdotes on them either cracking the glass or denting the trunk if you mount it to the car body. And anytime you want to ride then you gotta back the car out into the driveway, get the seasucker, make sure the glass is clean, install it x2, take the wheel off the bike, mount the bike, strap the crank so it doesn’t spin into your roof, and make sure not to forget the front wheel…and do all that in reverse without driving into the garage when you get home. Eventually I want to put a “stealth hitch” on with a 1up…seems like the simplest/cleanest/cheapest/most efficient way to haul a bike with a TM3. I believe you can buy a model Y with a hitch already on it. Otherwise it’s like $300-400 to get an aftermarket one that mounts to the frame.