I personally would go for this one:

Intellijel Quadrat
https://modulargrid.net/e/intellijel-quadratt-1u

None of your VCOs are stereo, so you don't need the stereo submixing, and the Quadrat can mix CV as well as audio.

If you find you don't have enough mixing, you can still add another mixer later.

1u buff mult - yeah go for it. I see no advantage in the Add 2.

Swells and Batumi are both good choices.

Further down the line, some envelope(s) would be good, so you can get some filter movement or effect to move with the sound.