You can put a lot of stuff in it, but it's *HUGE*, so you will not be able to fill it to the brim with furnishings. The 700 slots you will have with ESO+ are rarely enough to furnish one of the *HUGE* homes.
I'd rate Princely Dawnlight Palace up there with Colossal Aldmeri Grotto, Grand Psijiic Villa and Thieves Oasis as the ones which are very very difficult to furnish completely.
ZOS has improved on this a lot with the size ratio of more recent homes.