Message queue per user

I am using the same user to connect 4 servers to a database. Although the database is not overloaded, I think that if a heavy query delay occurs on one server, the other servers are affected, especially for new connections. Mysql server accepts up to 4030 simultaneous connections and has no query limits per user. Does Mysql queue the queries of the same user or those of all? If I create a mysql user for each server will I better optimize user queries and queues? Thank you so much.