OK, having had a look at X3 to check...
In the PRV (piano roll view) there's a pull-down below the keyboard graphic that by default says "velocity". If you pull that down it allows you to insert any MIDI CC number you want. You draw them in below the notes the same way as drawing/editing velocity. The + symbol by the pull-down does the same thing.
As for envelopes, yes, you simply insert a MIDI track envelope with the CC number you want.
The step sequencer is very similar in how it works to the PRV, wth the exception you can't add a CC where there isn't a note, which is a bit limiting as you can't program in a smooth sweep through values between notes....
As for MIDI controlled analogue synths, I've a Mopho which allows control of everything via MIDI, and sends CCs as well as receiving them. As far as I know the Tetra is the same. It has to be said that the third-party editing software makes programming the DSI synths much easier - not really enough knobs on the desktop boxes for easy programing, though they work well enough as performance controls.
As for the bass station, I've read the manual but it was a while ago and I can't remember what it's exact MIDI capabilities are. I once had an original which expired many years ago (the build quality wasn't exactly of the highest, but neither was the price of course) so I was interested in the new version. Might get one someday....
Might get an Arturia as well at some point. They're unique-sounding synths, especially with the way they mix oscillator waveforms. The Microbrute's patch panel is an asset as well. Being 1 volt/0ctave means it should interface OK with the lots of other gear such as the MFB and Doepfer range.
Thinking about it, I'd always suggest downloading the manual for any music technology you're thinking of buying before you buy and going through it carefully first. The MIDI spec is also always worth looking at.