IIRC, when you disable UDP Graal falls back to TCP to transfer data. UDP is faster than TCP, but only because UDP skips certain data checks and handshaking in order to achieve that extra speed.
I had a lot of issues with UDP though. Namely, with UDP enabled, in some cases I'd enter a room with a bunch of players inside and see most players moving but one or two players standing completely still in the position that they were in when I entered the room. I couldn't hurt these players and with clientside damage they couldn't hurt me either.
When one of these "frozen" players entered the room after I was already inside their character would be shown stationary in the doorway, essentially trapping me in that room because I couldn't hurt them.
After being banned several times for "hacking" I made a video of the phenomenon and Era eventually made all their damage serverside, which meant frozen players could kill me now, but I still couldn't see them moving or shooting me and couldn't fight back.
Upgrading to cable and disabling UDP fixed the issue for me, but now I also occasionally get the "Your Graal is running slow..." error as well. My ping is usually between 250 and 400, but even during sessions where I have a consistently high ping the chance of the error appearing seems random. I think it may have to do with only the speed at which you are uploading your character's position?
P.S. "wireless cable" is an oxym0r0n.