You can and should reduce hub drag with a spinner. You may not get more drag from the tips, depending on prop speed and design. You could end up with less in most situations with the right prop.

You can basically prop any engine for whatever RPM you desire, be it 2 bladed or more. You have prop design, pitch, and diameter to choose from.

Aerodynamically, you do have more frontal drag with more props unless you reduce prop diameter when going from one to the other. That is one reason pattern guys like them for the down lines at idle. Likewise, they like the pull for up lines. A 3 bladed prop may assist in a stable idle. I'm not sure what gyroscopic effects a 3 bladed prop will have over 2 blades. P factor may be more evenly distributed along the fuselage and fin with 3 blades.

The statement that all 2 bladed props are more efficient than 3 or 4 blades is sort of ignoring what a person wishes to do. A 2 bladed prop is not as efficient in the climbs or for descent braking as a prop with more blades. I suppose that a case could be made for a racer needing only 2 bladed props....