Most of my routing was done for Motorcycle rides / trips. Creating a route for a area close to home really wasn't a problem because I had already been on most of the surrounding roads and only wanted to try connecting via a "new way". It did get trickier when going to places I had not been. But I did not find issues with points or waypoints on roads (we liked country roads) as long as the point was on the road. I.E. if I was on extreme right side of road but GPS point was actually on left side of road, the GPS figured out that we got to the waypoint and went on to the next one.

Having said that, in some cases, we HAD TO TAKE A DETOUR around where a waypoint was. The following depends if your GPS unit has this (these) abilities.
1) while on the detour, I would recalculate the route from my current location. I.E. try to get to the next waypoint.
2) Some GPS until would automatically recalculate, but always trying to get back to the point that was LOCATED ON THE DETOUR. In this case, I would tell the GPS to SKIP THAT POINT and it would recalculate the route.
3) I had one occasion on REALLY back roads in West Virginia where several waypoints had to be skipped. We had NO IDEA where we wound up once we got to a major highway about 30 miles later. I took a guess, and told the GPS to go to a waypoint further down the route. This is like starting over from your current position. Once I got to the waypoint, I switch back to the route we wanted.

Having to quit motorcycling, I'm now into Trikes and have acquired a Edge 1030. But do not have the experience with it as yet to tell if any or all of those things are possible. Sorry.