The Task Manager in Windows shows a live per app view of network data traffic. When using Proton VPN, all network activity is aggregated and listed as data traffic from Proton VPN.

It would be nice if you could see the per app usage in the Proton VPN app.

When the current download or upload traffic is uncommonly high, I would usually check which app is responsible, perhaps you might want to stop the process. Currently, you have to guess what causes the traffic.