What method do I use to synthesize propyl-2-(2-methylpropyl)-ether and why?
There are two basic choices here if you are trying to do this on a lab scale. The alcohol plus alkene with catalytic acid is not an approach I would consider unless I needed a lot of this. t-BuOH plus acid is a recipe for isobutylene. Sodium or potassium t-butoxide is commercially available and reacted with an excess of iPr-I should give a decent yield of the ether.

The other approach is to use t-Butyl 2,2,2-trichloroacetimidate compound details here - a general reagent for the formation of t-Butyl ethers originally reported by Armstrong et al, Tet. Letts 29 2483 (1988)