Using Pi4, the OpenVPN maximum bandwidth I can see is ~100 Mbps (CPU is unable to handle more, and unfortunately, OpenVPN is single threaded... would have been really cool to have 400 Mbps of VPN throughput)
Without VPN, 1000 Mbps of fiber connection is handled without problem (981 Mbps according to Gnome System Monitor), using AX88179 USB3 for having a second Gigabit Ethernet port