Welcome!

Yes, you can get the full benefit of your Ensoniq sounds because a soundcard (wth respect to MIDI data) merely acts as a transmission station to get instructions from BIAB over into your synth.

BIAB primarily outputs MIDI which isn't sound or a sound file but instructions in code (like Morse code) that MIDI compatible equipment and software can 'read' and respond to, making sounds in ways the code has stipulated.

If your Ensoniq has some great synth sounds then if I were you I'd familiarise myself with the part of its manual that deals with MIDI. You also need to familiarise yourself with the concept of GM, or General Midi, which is the universal standard for 128 fundamental MIDI sounds with 1 being a piano.

Your soundcard probably has a MIDI in and out, so you can first connect its MIDI out to the MIDI in of your Ensoniq. That's the first step to getting BIAB to 'play' your Ensoniq's sounds. You may need to find/create what's called a Patch Map so that BIAB can address all the sounds on your synth.

There's a lot more, so I won't bang on! This PG site has tutorials on many aspects of the above. Have a browse around 'Support'. There are some bits and pieces on my bio web site also that may point the way, start here.
Best wishes - you've started your never-ending, at times frustrating, but by and large very fulfilling, journey into the wonders of recording!

John

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BIAB 2019
Cakewalk by BandLab
Studio One 4