HELP: Wireguard and OpenVPN cap out at 23mbps

[oiwruk]

Hi, I am running Proxmox on a HP Thinclient T630. The internet connection of the server is 100down/50up but over both WG and OVPN I get maximum 23-25mbps either way. I tried them in both a VM and a LXC with no change. I played with the MTU from 1420/1500 all the way to 1200 - again no difference. The CPU usage barely moves when I run the tests, so the bottleneck is not there.
I used to run a Thinclient T610 before which is much weaker and yet it gave me 45-50mbps downloads over either WG or OVPN. The only things that are different between the two setups are:

• now I use Proxmox, so the services are virtualised when before they were on the host.
• now there are 2 Fritzbox routers in a mesh (7530 and 3490) between the server and the Internet now (all wired) . Before it was a cheap TP-link C6.

In fact, before when both T630 and T610 ran OMV with the VPNs on the host and I used the TP-link router there was no discernible difference in VPN speeds between them. My suspicion is that the issue is the Fritzboxes because the speed tests ramp up very very gradually instead of jumping. Here is what Fritzbox say about MTU (link):

The FRITZ!Box does not offer the possibility to adjust the MTU size manually. This is also not necessary because the FRITZ!Box supports MSS clamping (Maximum Segment Size) that automatically adjusts the size of the data packets to the smaller MTU of the interconnected networks.

How could I troubleshoot the source of the problem? Sadly, I don't have physical access as everything lives in a family house away from me.
Many thanks

 

[bobmc]

The type of NIC emulation can make a difference in a VM but in a container the network should be at or near line speed.

Can you give a bit more detail about the meshed router config?

 

[oiwruk]

The type of NIC emulation can make a difference in a VM but in a container the network should be at or near line speed.

Can you give a bit more detail about the meshed router config?

Thanks for the reply! Yeah, it's strange that both VMs and LXCs as well as WG and OVPN all cap out at the same value without a CPU bottleneck.
The mesh is just the what Fritzbox provides - link. The 7530 is the main router, 3490 is wired to it and is a mesh slave. The server is wired to the 3490 through a switch.