What everyone else said. You are already too qualified for driver trainee. Make sure you get your endorsements before you apply cause some places will not consider you without them.
As for backing, linehaul doesn't really do much of it. You go from one terminal to another and your backing may consist of building sets/triples and then maybe backing to a dock in an open yard. Some places make you drop your trailer(s) and have their yard hostlers take over backing them in for you.
If you want to do linehaul, get ready to work nights. Daytime runs exist but are so scarce that they are considered the Holy Grail of runs.
If P&D is more your fancy, you will be required to execute extremely complex maneuvers at time. Alley dock is standard. But realistically you may find yourself backing in a complex pattern around cars, dumpsters, across multiple lanes of busy traffic, uphill while it snows. "I don't feel comfortable going in there" is an excuse that will get you ostracized by your colleagues and management.