The Opus card is shorter than the big Soundscape cards, but longer than the VIVO. One of the chips on the card says "OPUS" right on it. I was using it for a bit because it is a lot shorter than the Elite and S-2000 which didn't fit in one of my cases.
There are some catches to that card though. It is PnP and uses a wave port address that's not in the usual Soundscape range. Some games won't let you choose the port it uses, for their native Soundscape option. With Crusader, for ex, I had to edit the game's .cfg file and put the port in there manually. Also, its MIDI patch set is a 1MB ROM that's not that great. This patch set may be worse than the VIVO's as it is older but also the same size. Not positive on that though, but it is better than a SB AWE. Otherwise it is probably the "3rd best" Soundscape card because it still doesn't need EMM386 or use any TSRs.
It uses the same drivers as the original and Elite. This was not actually official though, because it is a Gateway-only card. I have had occasional issues with the Win9x installer. It seems to have problems detecting the card in some way and it doesn't always work. A manual install by pointing device manager to c:\windows\temp, while the installer is loaded and its temp files still in there, gets the job done though. The DOS driver "just works", once you give it the right port address.
I'll try to get a measurement for you later. But it's really not much longer (if at all) than an older SB16 or a AWE64.
For SB emulation, only the AudioPCI can do SBPro. The others are limited to SB 2.0 (mono). However, because lots of DOS games from 1994 onward support Soundscape natively, they can do the job quite well and their analog signal quality is much better than any SB I've ever heard (AWE64 Gold seems decent though). Their MPU-401 support is basically bullet-proof, unlike some other cards (SB AWE!)
If these cards only had a daughtercard header....