Why I did this:
- Install Wireguard to run WeVpn via router
- Setup a WiFi mesh in my apartment to increase range
- Play around with OpenWrt for the 1st time
I chose the Archer C6 v2 because it was cheap and I never had anything to do with flashing routers. In case I bricked anything it wouldn't be a big loss. Also my ISP doesn't really offer huge speeds so the Archer is more than enough.
ad 1: Flashing and setting up went well but speeds are not acceptable. But this was expected. It's about 50 Mbps instead of 150 Mbps when I run WeVpn directly on the Windows app. Also I thought I could switch from VPN to "normal" internet connection relatively quickly on the Lucy dashboard. But afaik this is not reasonable because there are several configs to make. Please correct me if I'm wrong.
Does anyone else have better speed experiences with other VPN protocols other than Wireguard?
ad 2: It kind of worked but mostly it didn't. Biggest problem is the Archer hasn't got enough storage capacity. I could flash the WPAD Mesh plugin at first but after setting everything up with another mesh router Lucy wouldn't take setting changes which is often due to lack of disk space. Only way to get more space is to build your own image with less components but I'm too inexperienced for this yet.
When it worked the speeds were ok. I reached 80 Mpbs.
Finally I connected the routers via LAN configured them as dumb access points and achieved the Wifi range increase. OpenWrt wouldn't have been necessary for this but I learned a lot which is always good 
Hope this is useful for some users. If you have any suggestions what I could do further with other plugins please let me know. Open for experiments.