Always cockpit view if it's available. It's not perfect but it's still the nicest view, perfectly driveable and best for immersion.
Bumper-cam gives you too much visibility and is in a weird position as well as making every single car look the same(but it's not too bad if you're in a standard). Roof-cam looks almost like a common TV camera, but gives a birds-eye-view of the apices, and tends to feel like you're driving an R/C car or something. Chase cam is nice to look at your car for a moment, but odd driving from, too much view and just looks like you're playing a game like Burnout.
I can never seem to decide on a zoom level, though. The wider views often seem to show nothing but your roof and make it tough to read the gagues, but from the zooms you lose a bit of the sense of movement, as well as being able to(sometimes) use the mirrors. Plus sometimes it's so close you can't see the dials anyway.
Once you stop paying attention to them the pillars/wipers/etc won't affect your driving one bit.