Shadowsocks is defunct now. Has been for a while; a connected server's IP can be detected and blocked within hours. That means Outline's defunct in a lot of places too. What's currently 'hot', in large part, is v2ray [1], be that vless, vmess, trojan, etc.
I'm not familiar with the software, but according to Wikipedia it's a client to connect to a SOCKS5 proxy:
> Shadowsocks is not a proxy on its own, but (typically) is the client software to help connect to a third-party SOCKS5 proxy, which is similar to a Secure Shell (SSH) tunnel.
that's oversimplification. raw socks5 is a low-level thing without encryption.
shadowsocks puts a solid cryptolayer on top of it, designed specifically to be hard to detect. its Chinese origin gives a hint here: it is created to circumvent detection by "great firewall"
outline builds a user-friendly toolset on top of it
Outline/Shadowsocks has better chances to keep working (though it is not a true vpn, more like a private proxy) https://getoutline.org/