I’m pretty sure OP is asking about forcing containers to use the VPN through gluetun.

“If I set up qBittorrent and the Arrs as Docker containers, can I use Gluetun to bind just them to the VPN?”

Yes, that’s what Gluetun is for. You create a Gluetun container and specify which containers should use it as the gateway in the compose file with:

network_mode: “service:gluetun”

Then you can open a shell in the container and run this to see if the container’s IP is different from your own:

curl ifconfig.io

Make sure to try stopping the gluetun container and confirm your other containers lose network access.

There are plenty of guides about this if you search for “gluetun arr stack”, like this random one I picked: https://www.smarthomebeginner.com/gluetun-docker-guide/

That has some steps outlining the basic gluetun configuration, how to put specific containers behind it, and test it.