Giving the wife a walkie talkie is an excellent idea. I have found when backing a larger vehicle of any type the headset walkie talkie with VOX works best so I have both hands free. A good policy is if in doubt, get out and walk back to see clearance you have.
The size of your RV will depend on the size you need based on the size of your family etc. Although I have had a 34 MH and a 32 ft 5Ver I full timed in there was just the two of us so it was large enough. Present day on short trips with the two of us a 19 ft TT is large enough. We can get into almost any NF camp site in and around Wyoming. If you get a 40 ft TT I suspect it will be for RV parks only. You have to decide where you want to camp and the size you will need.
Being careful, after a few miles you will start to feel more comfortable with a larger TT. Driving is different with any RV. You have to be more watchful of the smaller vehicles that have no idea of your stopping distance. That means more driving in the right lane, keeping more distance between you and the vehicle in front. It is like learning to drive all over again. You have to anticipate more what the other vehicles are going to do. When you pull in to fuel up you not only have to plan an entrance route but also an exit route before you drive in.
