As stated above, make sure to bind Qbit to your VPN's ethernet adapter.
Other than that setup search plug-ins/Jackett and enjoi the best torrenting software there is.
If you have a hard drive as your main storage, and in particular a raid array of smr hard drives, it's worth checking the 'pre-allocate disk space for all files' check box in the connection settings. it keeps disk fragmentation down and lowers raid thrashing a shitton when downloading large media files. You won't notice if it's just you using your one hard drive, but it made a huge difference on my raid5 smr setup.