Just wait for wireguard VPN! Here are my results with clean LEDE on AR300M-Lite (iperf3 through wireguard tunnel between AR300M and a local test server):
root@LEDE:~# iperf3 -c 10.0.10.1
Connecting to host 10.0.10.1, port 5201
[ 4] local 10.0.10.3 port 50784 connected to 10.0.10.1 port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 6.43 MBytes 53.9 Mbits/sec 0 123 KBytes
[ 4] 1.00-2.00 sec 6.50 MBytes 54.5 Mbits/sec 0 158 KBytes
[ 4] 2.00-3.00 sec 6.56 MBytes 55.0 Mbits/sec 0 176 KBytes
[ 4] 3.00-4.00 sec 6.44 MBytes 54.1 Mbits/sec 0 186 KBytes
[ 4] 4.00-5.00 sec 6.50 MBytes 54.5 Mbits/sec 0 195 KBytes
[ 4] 5.00-6.00 sec 6.50 MBytes 54.5 Mbits/sec 0 206 KBytes
[ 4] 6.00-7.00 sec 6.62 MBytes 55.5 Mbits/sec 0 206 KBytes
[ 4] 7.00-8.00 sec 6.50 MBytes 54.5 Mbits/sec 0 206 KBytes
[ 4] 8.00-9.00 sec 6.81 MBytes 57.1 Mbits/sec 0 291 KBytes
[ 4] 9.00-10.00 sec 6.44 MBytes 54.0 Mbits/sec 0 291 KBytes
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-10.00 sec 65.3 MBytes 54.8 Mbits/sec 0 sender
[ 4] 0.00-10.00 sec 64.5 MBytes 54.1 Mbits/sec receiver
iperf Done.
root@LEDE:~# iperf3 -c 10.0.10.1 -R
Connecting to host 10.0.10.1, port 5201
Reverse mode, remote host 10.0.10.1 is sending
[ 4] local 10.0.10.3 port 50788 connected to 10.0.10.1 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 7.79 MBytes 65.2 Mbits/sec
[ 4] 1.00-2.01 sec 8.71 MBytes 72.4 Mbits/sec
[ 4] 2.01-3.00 sec 8.31 MBytes 70.5 Mbits/sec
[ 4] 3.00-4.00 sec 8.69 MBytes 72.9 Mbits/sec
[ 4] 4.00-5.01 sec 8.68 MBytes 72.5 Mbits/sec
[ 4] 5.01-6.01 sec 8.44 MBytes 70.6 Mbits/sec
[ 4] 6.01-7.02 sec 8.78 MBytes 72.7 Mbits/sec
[ 4] 7.02-8.00 sec 8.34 MBytes 71.3 Mbits/sec
[ 4] 8.00-9.00 sec 8.60 MBytes 72.0 Mbits/sec
[ 4] 9.00-10.01 sec 8.44 MBytes 70.2 Mbits/sec
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-10.01 sec 86.3 MBytes 72.3 Mbits/sec 0 sender
[ 4] 0.00-10.01 sec 85.3 MBytes 71.4 Mbits/sec receiver
iperf Done.