power supply design

should i wire switch before or after relay or it doesn't matter

and where do i need to put my fuse on,input or output side of relay

I don't understand your question about the switch -- it would just need to connect / disconnect one side of the relay trigger circuit.

I normally put the fuse on the input (power feed) side of the relay.

Normal use is power to fuse, switch, device being powered, ground. Sometimes it's power to switch, fuse, device being powered ground.

the reason the switch and/or fuse should be placed closest to the power supply is because the protects most of the circuit and/or the switch turns off the power to most of the circuit. I guess you could place the barts of the circuit in any order, if you wanted, but it's not the smartest idea.