I have read some questions about using both TCP and UDP in multiplayer game, such as Does it make sense to use both TCP and UDP at once? and Is UDP still better than TCP for data-heavy realtime games?.
Most answers recommend against using both at the same time, and maybe use a reliable UDP library, because of the TCP induces UDP packet loss argument stated in this paper for example.
But, if I don't use them both at the same time, e.g. using TCP when the players are still in the lobby/room and then sending data like who are in the room, players data, who just joined the room, etc. where everything must be reliable but also pretty infrequent and then as soon as the game started it switches to UDP to send data like movement, position, etc. where some packet drops is okay, is it okay to do this?
What about if the server is currently handling multiple games at once, like one game is currently playing (using UDP) and another one is still in the room (using TCP)? Will there be a massive packet loss for UDP?
Also about the simultaneous TCP and UDP packet loss, is it only happening if we use them in the same port or does it still happen regardless?