FINALLY was able to do some testing.
Basic IPSEC connection from AX Lite to RB5009 (AX Lite → ISP Router acting as local switch → RB5009 so all Gigabit connections).
Both devices on 7.11b6
Used iperf from PC connected to AX lite to iperf container on RB5009.
Max I saw was 58 to 65 Mbps (did several tests).
CPU on AX Lite went to 76% (1 core to 85% so not yet maxing out).
RB5009 never went over 17%.
Better then zerotier (because of HW offloading ?) but way below wireguard. Still a huge difference though …