The minisuites aboard MV Sun Princess are basically somewhat smaller versions of the full suites. Any of them should be plenty large for two adults. Their layout would be good for two adults who are not sharing a room, as the head is accessible from either the bedroom or the sitting room without passing through the other. IIRC, the balcony also is accessible from both rooms and there are separate televisions.
I think that the aft minisuites are pretty similar to the minisuites loaced on the side of the ship.
If cost is a concern, you might be able to get two standard cabins for less than the price of a minisuite. This would have the advantage of providing separate safes.
If you don't mind sharing a room but want separate beds, any standard cabin could accommodate you. The beds in the standard cabins are configurable as either two twin beds or queen bed.
If, OTOH, you want to enjoy the suite life and don't mind paying for it, enjoy!
Have a great cruise, whichever you decide!