Thanks everyone! The horizontal surface was used as the cart was in progress. Glad we went with this design rather than a more vertical "tower" as some have used (obviously that's a good option if floor space is limited).

With the minisplit in place really wanted to deal with dust. I do have a Jet scrubber up above and added a pre-filter above the MS (does not seem to impact the air flow with 4" filters).
In addition the wall fans also have 4 inch filters (these help circulate air into and out of the side room). One of those is shown in the first picture.

Still to come is dealing with the mitersaw. Working on a plan to add a box and just better setup overall. Currently have a cardboard box in place that I was using to get an idea of dimensions (actually that helps already).