Thisis very much possible with opnsense which we recommend using policy based routing and it has been on my to-do list to write a guide for that OPNSense split tunnel guide with VLANs · Issue #1863 · privacyguides/privacyguides.org · GitHub
I don’t know about those Asus devices or the Gl device, but the OPNSense offerings are very much capable.
There is a youtube here for doing it with pfsense https://www.youtube.com/watch?v=ulRgecz0UsQ