I use Garmin RV navigator. If I'm going through big city I may check the route on navigator vs. what I see on map. Sometimes there is highway rings around the city, some may be newer and larger than the ones through the city core. Sometimes :) I'll occasionally override the navigator and let it recalculate. Strongly recommend RV GPS navigator.
Best time through is often Sunday morning before 6:30 AM if possible. IMO very heavy slow traffic on highway isn't all that hard to drive in, it is just a time waster.
If driving through the city core on surface streets I will generally plan and research the roads in advance. Starting with navigator suggested route. For me it doesn't happen often-most of my camping is not in downtown city cores.
Newer suburbia generally I don't find challenging. Wide roads, shoulders, newer businesses with big parking lots.
Probably my least favorite RV driving condition is in some construction zones. K rails, cones, erratic lane width, erratic corners, poor signage, etc. Toss in crazy drivers whoo hoo!