We are booked in E728 and E731 for Alaska in June and I have been hunting for specific info on these rooms. Here is a couple comments from someone that actually stayed in the room:
the minisuite (E731) is set up exactly like the minisuites in the Grand class (the desk is at an angle, not straight like on the Coral Princess) The upholstered panels, matching the bedspread are a nice seafoam and cream, nothing garish (as I found the standard balcony's fabrics to be, but that's just taste). The chair in the living room of the mini is nicer than that of the grand class. It had a natural rattan like back, and a tan leather seating surface (probably vinyl, but done well) and the same seating surface is found on the desk chair. Felt more upscale than the Grand or Sun class cabins. Fabrics were richer, carpets a higher quality.
I know I'm spending a lot of time talking about 'soft goods' as they call them in the cruise industry, but it really seems to me that this is where the main differences lie between the Diamond class and others. I had no need to use the couch as a bed, but was surprised to find that it was different from what had been described about grand class mini suite couches. This one actually folds out, but only the two pillows closest to the sliding glass door need to be removed for this fold-out to occur. In other words, the bed that folds out is not the whole width of the couch. It may be a 'single' bed, but I didn't measure it. The couch was more comfortable than the minis I've seen on other Princess ships, again with richer fabric and padding. The balcony is SPECTACULAR though, and has room enough for a cocktail party of ten or more (if you folded up your outdoor furniture and moved it to one side).
And another comment about these rooms:
Hey everybody, just to answer the question about E731 (mini). My friend and I, traveling as 'singles' were in rooms E731 and E735 (aft BB). Absolutley NO noise whatsoever except on Deck party night when the music from above could be heard - but not anything awful. I was really concerned about noise, and there was real POUNDING disco music going on in club fusion at times, and when I would be walking down the promenade deck and hear really loud music I would run upstairs to my cabin, close the sliding glass door and lsiten. NEVER did I hear a thing. I was shocked. Soundproofing has been perfected!
As far as converting twins, yes, both configurations are possible and it IS a tub/shower combo.
I also found a picture of the balcony from the outside of the ship. You can see the deck is about twice the width of the other mini-suites, but it does not "wrap-around" the ship.