I leave mine in a heated garage most times, at around 12C. There is nothing special about range loss. It's minimal once the car sleeps.
You can preheat the car anytime, plugged or not. I don't preheat it personally because it's already warm but I am missing some regen. The floor gets cold so the battery is closer to 6C than 12C when I leave in the morning. Preheating would take care of that. My drive is too short to bother.
Being plugged in just means your battery won't go down while preheating.
The bad news; my garage rarely gets too cold, (rarely under 16 degrees) and I still face a cold battery pack if I don’t prep the battery before driving by charging it. If you drive regularly, the scheduled end time makes this way way way more painless today than it was years ago.
The good news; range loss is going to be big (30% or more) for any short duration trips no matter what you do. Right, but the good news, if you do long trips or drive for long periods of time it’ll even itself out. Mostly, this is a none-issue because when you’re doing a lot of short trips you probably don’t need the full range of the car because you’ll be back home. If you are doing a road trip elsewhere, the range loss will be less evident because it’s only the first 20 to 30 minutes where it hurts you the most.
So really, it’s more about assessing your needs. I don’t want to make any assumptions on how you’ll be using the car, but for 99% of drivers, this is unlikely to be an issue (though there will be lots of posts from new Tesla owners upset they lost 50km of range after only driving 25km and worried this is how the range will be reflected for the rest of their ownership).
When buying a car and noting range, chop the bottom 10% of the range because you’re not likely to drive with less than 10% charge left on the battery. Chop the top 10% because you’re unlikely to charge to 100% daily (and shouldn’t anyway, the car will warn you). So you have about 80% of the range that’s usable. If you do a lot of city driving, you’ll have 2/3rds that range. If you do a lot of highway driving at normal speeds, you’ll have 4/5ths that range. When you’re done for the day, and plug the car in, you get it all back the next day.
Whether you’re in a garage or outside, prepping the battery for your drive by charging it will help with these numbers. Outside, it’ll cost you a negligible amount more in electricity to charge the car (because the battery will need longer to warm up), but overall you’re good either way.
If you really need to make an high efficiency leg during a winter road trip. Charge to 100% with a L1 or L2 charger overnight and hold it there for about an hour (preferably) in an indoor heated garage. I achieve near 90% efficiency one time when I slept in and the charger/car held 100% one hour past my departure time.