With a username and password, the login travels with every request and works from any network: your laptop, a server, a phone. With an allowlist, the proxy accepts any request that arrives from an address you registered, with no login at all.
PiratProxies plans use a username and password. The username also carries your settings: the country, the city and the session are written into it, which is why it is longer than a normal login. A wrong or mistyped login is answered with a 407 error.
Read next: Quick start