I have been running benchmarks on DigitalOcean with different droplets in different locations
When using encryption it's expected to generally have a reduction in throughput.

image="centos-7-x64"  size="s-1vcpu-1gb"  region="ams3"
image="centos-7-x64"  size="s-1vcpu-1gb"  region="fra1"

iperf direct-test:
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec   959 MBytes   805 Mbits/sec  637             sender
[  4]   0.00-10.00  sec   957 MBytes   803 Mbits/sec                  receiver

iperf IPSec-test:
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec   206 MBytes   173 Mbits/sec   15             sender
[  4]   0.00-10.00  sec   206 MBytes   172 Mbits/sec                  receiver

iperf WireGuard-test:
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec   481 MBytes   404 Mbits/sec   46             sender
[  4]   0.00-10.00  sec   478 MBytes   401 Mbits/sec                  receiver


Many things can come into play, optimizations, maybe crypto acceleration etc, but that's beyond my expertise.

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