4 pin relays for headlights

What size fuses should i hook it all up with. Should high beam be a different fuse than low beam? Can i assume use a 12 gage or a 10 gage wire from the battery to the relays? How about a fusible link?

Also since my relays will be in a sealed box i am looking at the non weather resistant ceramic 5 pin relay plugs. Not sure if theres a heat issue or not, or if regular plastic 5 pin plugs will suffice. Any recommendations?? Yes? No?