I think that the reason for not having an issue with the oil lubed pump might be that pump doesn’t run long enough to generate enough heat in the lube to volatilize it where it gets passed the rings and into the tank and onto the work.
Then too, oil may not be nearly the problem in shooting the types of coatings we are talking about here, as opposed to the automotive finishes that I learned on. I assumed oil would have a similar effect, maybe not? Still all in all if I had my druthers, and, I was buying a new pump I think I’d get an oil less pump just the same.
At the level of use it seems you will be doing Mike, I’d guess that the Makita should work just fine, it may run most of the time you are spraying do to the small tank capacity, but the pump on its own seems like it should keep up with demand. If you had to do a lot of work very quickly, things might be different, once the pump gets real hot they tend to lose efficiency and the 4.8 scfm could drop as much as 30% or 40%.