One thing we learned from camping in cold temps (and sorry if this has been mentioned already) – is that the basement bays won’t be kept above freezing unless the furnace is running, and while using space heaters up above, our furnace wouldn’t always cycle on. So, interestingly our water was more apt to freeze at 25 degrees than it was at 15 degrees, because at 15 degrees the space heater couldn’t keep up, and the furnace ran more, keeping the basement warmer. If that makes any sense. Bottom line, if the furnace isn’t running, the basement gets cold. That was the case in our coach, and I know not all coaches are the same in this respect.
Using your RV in the winter? Make sure you have a show shovel, window scraper and some kind of ice chipper (i.e. an axe). If you don't have these on hand, guess what? The first time out you will be sure to need them. Also pack a bag of rock salt (sand or kitty litter) to sprinkle on walkways and to put around your tires in the event you get stuck in snow or end up on slippery patches of ice.
So, just depends on the site and the park. Older parks often have smaller sites and tighter access than newer parks. Forest service campgrounds are typically tighter than desert campgrounds. I use rvparkreviews.com to help gauge these things, and combine it with satellite pics (Google Earth) and campsitephoto.com where it’s available. Between the three I can usually make a good guess if we can fit. It’s a process!
While neither of us were ever crazy planners, Kerensa did like to have a general plan of where we were going and what was around when we got there. Sometimes that skill still comes in handy like planning for the Florida Keys, but for the most part, we don't make reservations anymore. We prefer to stay loose with our plans and be able to adjust quickly to meet friends, dodge weather, or choose a destination on a whim!