My point is that even historic RB433AH, that I can do quick test with, can do ~20 Mbps with OVPN and ~25 Mbps with IPSec (without L2TP, but it shouldn’t make much difference). And that device has much weaker CPU than yours and no HW acceleration at all. So your problem is probably elsewhere.
Also, posting configs works better the other way, when you post yours and someone might spot what’s wrong.