I would take any manufactures claims with a grain of salt. In other words in my opinion they don't mean anything. Go to the tachometer forum and do a search and you will probably find some reading on the engines with different props that will provide some actual useable info. Naturally none of the posters on this site would inflate their rpm claims.
A 90 size is 1/3 larger than a 60 so it should have 1/3 more power. Doesn't work that way all the time as some engines are revvers and some are ported for larger props at a lower rpm.
I do not like anything super tiger so I would go with an OS or Thunder Tiger in a size that would give the plane adequate performance.
Fred