I have very little experience in that regard, my plan for heating has always been diesel. I know Webasto units are reliable having used them for years without a single failure, less experience with Truma but I hear good things, parts and servicing is reliably available here for those systems.
I was thinking to just have the gas under the sink with a spare one in the storage areas, but now I am having some fun designing my chassis storage bins (from
https://edelstahlhaus.de/) I am thinking to make a dedicated "propane" storage box-...