AR300M Shadowsocks max speed

I just subscribed to new vpn service to watch netflix. They planned to have wireguard this year and during the wait, I am exploring what options that they give. One of the options is shadowsocks, which I thought will be less encrypted and much faster compared to openvpn udp/tcp. After finishing the setup I did speed test and got 12mbps, faster than openvpn (max 8mbps) but compared to android phone that use shadowsocks too (with same vpn setup), I got more than 25mbps. Is it hardware limitations or I miss something in the config?

It is hardware limitation.

A smartphone is much powerful in computation.