Is Unet too heavy for mobile games?

I'm making a multiplayer game for mobile devices. It's 2D, It's collision based, without physics (something a bit like agar.io). Now Unet only provides me with p2p connections helped by a relay server. Which I think is horrendous for a game running on mobile hardware.

• But am I correct in assuming so?

• What could be a better alternative? I need something with good
  documentation cause I'm really new to networking.

• Also, what if I was to use my
  computer to run a couple of instances of the game, and keep them running as hosts 24/7?