Why OVPN? Have you not heard of The One True VPN Lord & Saviour, WireGuard?
Seriously though; WG stomps all over the speed of OpenVPN. It’s not even a fair competition.
Regardless, I think you’re going to want to see this: When tailscale is active the users of my guest WLAN (1800AX, 4.2.1) can´t connect to internet