BeetVPN vs Mullvad VPN

Don't trust forks much, As i rather put my data with firefox plus mullvad vpn works with them on their vpn service. And mullvad is a really good privacy vpn..

How would i go about configuring mullvad vpn in the 'proxy server' tab? is it even necessary? i tested a leak when connected to mullvad and there was none, but does filling in that tab make you more secure? How would i go about configuring mullvad vpn in the 'proxy server' tab? is it even necessary? i tested a leak when connected to mullvad and there was none, but does filling in that tab make you more secure? Also, when im on vpn, would i have to change my port? I tried testing if port was open on another site and it said it didnt work, but torrenting is relatively fine, although it seems like thats whats stopping a few peers from connecting. when i checked w/o vpn it said it was success, which is why im thinking i have to edit something there. Would i have to enable NAT as well through mullvad, or is that not possible?