You can look up the mod details for your current ship's equipment in outfitting, but if you're looking at your other ships via the shipyard, then you can only see if a module is modded or not, not their details.I think there isn't in-game, but if you're funning EDD or EDMC you could check your fleet and its load-outs on EDSM.
Also, about the Dolphin: it would be somewhat OP if it had a universal class 5 internal slot, but for passenger missions (which is what the ship was designed for) it's great that such a small and cheap ship can fit a luxury cabin. Those only come in size 5 and above.