I too use VLANs, both on router/firewall, and PoE switch
Those of use with such networking knowledge, know how to work around these sorts of issues, when needed (usually).
In the case of OBS Studio sending out NDI (completely separate from receiving NDI video feeds, which is what I'd assume (maybe wrongly??) that most OBS Studio users are using NDI for, manual (command line) adjustment to Operating System routing table to handle interface for a given output might make sense, but still presumes a non-overlapping network space.
Then again, takes a fair amount of traffic to flood a 1GbE network, and if that is the case, I'd be more inclined to keep it simple with 2.5/5 GbE 802.11bz or even 10GbE (which I do have here at home, though no SFPs at the moment ... awaiting new workstation)
And then again, if OBS Studio traffic is mission-critical, that has a whole other set of implications from video processing and power redundancy, to physical path divergence even at ISP level, etc. True mission critical gets really damn expensive really quick.
I love the one commercial datacenter facility I we had space in ... where the guards included many ex-special forces, and were nation state gov't authorized to commandeer fuel trucks, if need be, to keep certain generators (facility segments) running.