OpenVPN encryption issue

Hi,

i have a question for openvopn bandwidth on the encryption.. I am bulding a video play envrioment between two offices with multicast.

i built a client (RB450Gx4) to hub(AMDEPYC CPU 1VCPU+1G RAM) to client (RB450Gx4) infrastructure as diagram

i used two solution

1, EOIP on L2tp

2, EOIP on Openvpn.

With the same network link, when I use l2tp without encryption, the bandwidth can run a full bandwidth on 100Mbps on PC connecting with two cliens during the network bandwidth testing, and video plays smoothly. But when I use openvpn with encrytion, the bandwidth is lower than 30Mbps and can’t going up, the videol play broken, is there any configuration suggestion i can tune to improve the performance, or its the hadrware limittation?
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