I neither have experience with wireguard nor x/crypto. But I did some measurements on crypto algorithms for QUIC efficiency before. There I achieved about 350MB

I neither have experience with wireguard nor x/crypto. But I did some measurements on crypto algorithms for QUIC efficiency before. There I achieved about 350MB/s throughput on a single Ryzen 3900X CPU core using ChaCha20, compared to 500MB/s using hardware accelerated AES256. That might or might not be faster than your network. Note that the numbers include networking overhead, if you would just measure crypto performance the numbers would obviously be higher - as would the difference between the algorithms be.