Its kind of difficult to judge without knowing the construction details, but removing the chipwood floring, as then You can operate from the top, might be considering the total workload a good idea.
I like XPS over other foams because it (practically speaking)just don't collect any
moisture in any conditions, PU foam is not nearly as good in that respect.
Rockwool is OK, but much more work as one should use both windstopper(below) and air seal(on top) of insulation + something to carry the wool between the beams.
fun on a boat is inversely proportional to size...sort of anyway