But remember that WG runs on kernel mode, that is similar to NAT acceleration (aka hardware offload)
I think the blurb you pasted from Merlin above is outdated. When I got my AX86S in December 2022 running a WireGuard client did disable hardware acceleration however on 382.2.2 both Runner and Flow Cache are enabled and the AX86S passes 940/42 Mbps without an issue. I haven't had an opportunity to connect by desktop to the AX86S directly nor does spdMerlin have the option to test the speed of a WireGuard client.
7/14/23
ISP Internet 1200/40
VPN Provider - StrongVPN
I had an opportunity to runs some tests and compare the speed of an Open VPN client vs. WireGuard client.
All tests were run to VPN servers in Miami which is 225 miles distant.
Router Used was an AX86S with a two core A53 Cortex processor, 1800 MHz
For comparison I also tested using a mini pc setup as a VPN appliance. It has an I7 processor.
All connections to my network were by Ethernet cables.
OpenVPN AX86S Router 55 tests recorded using spdMerlin during July.
Download Average 175.6 Mbps std dev 28.1 OpenVPN Miami
WAN - spdMerlin Download Average 590.6 std dev 70.9 to nearby ISP
When speed tests are run on my PC then with no VPN tunnel speeds are often over 900 Mbps. If using my VPN appliance running WG with a tunnel to Miami then VPN download speeds often exceed 800 Mbps when connected to a WG server in Miami.
WireGuard client running on router the Speed Test being run on PC. PC connected to router with Ethernet cable. In the 388.2.2 version of Merlin's firmware hardware acceleration is enabled even when WireGuard is on.
I just had the time to run 5 tests in this setup and the downloads ranged between 220 - 235 Mbps.
My conclusion is just as many/most consumer grade router's processors don't have enough processing power to enable fast OpenVPN connections that even when running WireGuard they can do better, but most consumer grade routers still don't have enough processing power for fast VPN connections.
Hopefully someone with the latest and greatest router can repeat my tests and get more than 25% of their ISP's provisioned speed when running a WireGuard client on their router.