Thanks for the answer, I've been slow to give feedback because I was on vacation :)
It really gives me hope to see that both firmwares did well for you on the ac86u 2900.
I'm trying to find the right version of tomato but this router doesn't show up on either the DD-WRT or Fresh tomato...
I bought two routers last month, one from Gl.inet and an Asus RT-AC68U.
I see it is impossible to use my RT-AC68U router as a VPN client in router mode.
I want to connect my Asus router to my home router wirelessly and still be able to use OpenVPN or Wireguard, just like the little gl.inet...