Why is wireguard much slower than openvpn?

I've installed both wireguard and openvpn and I found out Wireguard is much slower than OpenVPN-AS with TCP.

And iperf3 bandwidth test shows wireguard supports around 20Mbps while OpenVPN-AS supports my max ISP bandwidth that is 160Mbps at the time of the test. It's almost 10 times slower.

What do I do wrong? I haven't done anything special, just installed, configuring and that's it.

RHEL 8, is there anything I need to enable?

Its configuration is pretty basic:

[Interface]Address = 10.111.0.1/24ListenPort = 51820PostUp = sysctl -w net.ipv4.ip_forward=1PrivateKey = XXXX# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~# Name:  office's server; PTP link# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~[Peer]PublicKey = 9e2nYnG/l6j....AllowedIPs = 10.188.0.1/32   # The endpoint itself via VPNAllowedIPs = 192.168.188.0/24  # The whole office's subnetEndpoint = remote.emea.xxx:51820PersistentKeepalive = 300# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~# Name:         alexis[Peer]PublicKey = gmb0Xdu...AllowedIPs = 10.111.0.2/32

I also see lots of lost packets:

Changing the MTU on the server and clients doesn't solve the retransmissions and therefore the low performance.