I got a Raspberry Pi 4 with 4GB Ram. 

I ran some benchmarks. With pure iperf3 I get 950 Mbit/s.

With wireguard in the same network I can only get max 750 Mbit/s (which in itself is already great).

In htop I can see that one of the 4 cores is running at 99%. So I assume that is the bottleneck.

Is there a way to improve this? I assume it does not matter which side is the server and which is the client?

Thanks,

Christopher