Mullvad VPN vs ProtonVPN

Talking about Express and others, Mullvad have the best speed during my personal experience. (I tried paid subscription to Ghost, Express, ProtonVPN and Nord.)

As the OpenVPN wrapping of the wire packet sent to the remote side then typically goes below 1500 bytes - which most of the Internet infrastructure mostly tackles just fine. Otherwise, if the TUN packet itself is 1500 bytes, the OpenVPN wrapping increases the packet size enough so the packet often ends up being split into two packets - which impacts performance. Now mssfix is set to 1450, which is helping - but only for TCP packets, not UDP.