Here is the configuration:

http {
limit_conn_zone $binary_remote_addr zone=limitapinoauth:16m;
limit_conn_zone $remote_user zone=limitapi:32m;

map $remote_user $limit_zone {
default limitapi;
'' limitapinoauth;
}

map $remote_user $limit_number {
default 100;
'' 200;
}
}

server {
limit_conn $limit_zone $limit_number;
}

When starting NGINX getting a fatal error though. Does limit_conn support using variables?

error => invalid number of connections "$limit_number"