Your proposed setup should work fine. I have a similar setup though I use a dedicated pfsense router. As for the use of a 10g switch I think you just need to make sure it can negotiate 2.5gig. Otherwise just make sure you put the main deco in front of your switch then you can wired back haul the other deco units to the switch, same as you have it shown in your post. The other main thing you might consider is if you are in a mid split upgrade area for Comcast. The s33 does not support the higher upload speeds yet for Comcast. Check out their approved mid split modem list if you want something that will support the 200mbps upload.

I have this 8 port with 1 sfp+ switch and it came with rack mount ears. I have the Poe version. https://www.amazon.com/gp/aw/d/B0C653X7M6?psc=1&ref=ppx_pop_mob_b_asin_title&th=1