What is the correct way to install a washing machine drain pan?
Go with your second approach of getting the right size fitting except don't bend the pipe, just deal with the angle. You pan lip should be higher than the ending (with fittings) top of the drain pipe so it can drain but that's all you need.

Why? PVC fumes are extremely toxic and you have a significantly better chance breaking the pipe than fixing the angle; then you'll have to tear up the floor to fix the pipe. A washer machine drain pan is used for worst case scenarios, not day-to-day use so as long as water can drain you'll be fine and a slight angle may actually decrease the minimum height of the drain anyways.

As for drilling the hole in the pan, mark it in place and drill it somewhere else with a sacrifice piece of wood/etc. underneath. You don't want to hold it up or anything because you'll need a decent amount of pressure to hold a bit in place and plastics like to fracture if not properly supported.