Yes, it appears Jenolan
is about the size of three(!) Constitution
-class ships in volume, or just under. Of course, a lot of that is probably empty space for carrying stuff, and she sure could carry a lot of it. Some fans assumed that she was only a personnel transport because she was carrying Scotty and because the Nash
was conveying various important characters on four occasions on DS9, but I rather think this type of ship is a heavy warp hauler that can carry lots of cargo and passengers too, and this probably explains why we see one in active service many years later (even heading out to relatively distant and dangerous DS9). I don't think she could land, being so big and considering the time she was built, but there's definitely plenty of room for shuttles to come and go.
It's possible Geordi was being a bit nice when he estimated its impulse performance relative to Enterprise-D,
but I bet he actually has a point, and I take the statement about impulse engines not having changed radically at face value.