Same issue found with zerotier.I actualy noticed the same thing from my phone can't get more then 20mbit with 4011 on other side and s21 ultra as client, also same version routerOS, gona try older versions tomorow I tried about everything else today from changing MTU, completly disabling any firewall rules or queues, nothing made difference.
I just tried very same config file from my phone on Windows 11 laptop wireguard app and im getting full speed (around 70mbit which is max of my line), even running hotspot from my phone to laptop again full speed over phones net.Doesn't that make you wonder?
Hmm... IIRC, I only got 40 mbps with wireguard between a HEX and a CCR2004.Site-2-site from hEX s to RB4011, with iPerf3 I get up to around 150Mbps which is which is max throughput capped by ISP. No tuning of Wireguard at all, both sites are running 7.3(.1).
And how do these phones perform with regular speed test ?...Doesn't that make you wonder?
I also tried 3 different Samsung phones(s10+, s20, s21 ultra) and via different nets and also cant get more then 20mbit.
Must be some issue with phones or their latest software...