I think you can achieve the example you’ve shared here:
using Netlify Redirects as well. Here’s how:
Connect eviltwins.studio and experiments.eviltwins.studio both to a single Netlify site. In that Netlify site, add the following redirects:
[[redirects]]
force = true
from = "https://experiments.eviltwins.studio/*"
to = "https://eviltwins.studio/experiments/:splat"
status = 301
[[redirects]]
force = true
from = "/experiments/*"
to = "your-webflow-url/:splat"
status = 200
This way, when someone hits experiments.eviltwins.studio, they will be (301) redirected to https://eviltwins.studio/experiments/ and then, the second rule will take care of the proxy to Webflow. You can then remove the 301 from Webflow.
Not sure if I’ve missed something, in which case, apologies and feel free to point out.