I just tested this VPN on my Comcast Gigabit Internet speed, which is about 1,000 Mbps and that is with an Ethernet wired connection.
I have my laptop connected via 5G WiFi and here are my test speeds at http://www.speedtest.net:
Without VPN my normal speeds are: 533 Mbps down, 40 Mbps up.
With this VPN my speeds slowed down a bit to: 339 Mbps down, 38 Mbps up.
I also did a wired connection test:
Normal speeds were: 916 Mbps down, 41 Mbps up.
With this VPN: 620 Mbps down, 40 Mbps up.
I think these are acceptable speeds as ALL VPNs do slow down, of course the less slowdown the better.