I’m a new Mullvad user. I can say it works good for me but one drawback is the fact that Mullvad’s servers are flagged by most geolocating streaming services (free ones, like iPlayer). So I wonder if I can use safely Chrome browser extensions (like Windscribe and Hola) just for these services with the Mullvad app turned on at the same time. Because I don’t know if these extensions connect through Mullvad or bypass it. I don’t want them to know my real IP because I don’t trust Windscribe (US-based) and Hola (this one collects a lot of personal data for sure) as I trust Mullvad.
Mullvad. Good for security, good for privacy, bad for streaming.
Best option may be to run a 2nd VPN.
Windscribe is a canadian company and it’s also pretty transparent like Mullvad.
Just don’t forget to turn off webRTC and you won’t have any IP leak
That’s exactly what he’s asking about.
correct me if i’m wrong but i thought webRTC leaks were no longer a thing (https://www.reddit.com/r/uBlockOrigin/comments/scii67/why_webrtc_option_is_removed/)
Hopefully OP sees it’s exactly what I’ve answered, then 
Actually, what I really seek to know is if the traffic generated by the browser extension is also tunneled through Mullvad before reaching Windscribe or if it bypasses Mullvad by creating its own tunnel.
If this traffic was effectively tunneled through Mullvad, it would create a kind of double-layered protection. It depends on how these extensions work.
What you seek/hope to find is called “Split Tunnelling” and the capability to do so would be explained in the notes to the browser extension. You’d need to look on github, etc.
I doubt that it does this. Services that can, are typically not free, and those that are “free” are compromising your data. IMO/YMMV
For $5/mo you could have certainty by choosing a different VPN.