My wiring kit (4awg - 20mm2) came with a 60amp fuse.
I wouldn't put more than an 80 on to be safe. You can always uprate it if it goes. but you can't replace your car as easily if the wiring fails. Everywhere on the net recommends a 60A maximum on 4awg power cable too.
If I was wiring 2 amps, I'd buy one of
these for the positive battery terminal and put seperate inline fuses just after, specifically rated to each cable.
It'd mean drilling an extra hole to run the cable but surely it would be safer in the long run?