4G with VPN mean that the packet comes from the mobile network via WAN encapsulated in l2tp, gets extracted from there and goes to the real destination via the same WAN (or vice versa for the opposite direction).
There is no difference at Mikrotik side between a PC connected using a cable and an external AP connected using a cable, so if the performance differs between these two cases, the limitation must be outside the Mikrotik. Interference in the air is the hottest candidate, that’s why I have mentioned it first.
Another candidate for the bottleneck could be the phone’s CPU, but a much less likely one.
The computer in which the speeds are normal (wired). When I connect it to the VPN in local network. Then my speeds are 80/100 so…yeah…pretty sure it’s a mikrotik problem.
No problem when I use wired connection on PC1. No problem in PC2 when wired. Problem when using wifi on phone. Problem when using wifi on PC2. Problem when using 4G on phone.
With 4G yes, the packet comes from the mobile network via WAN encapsulated in l2tp BUT download speed should still be better than upload speed. Or when download speed is not better then download and upload should be equal.