Otherwise the brake system will be TRW and will have two bolts with standard hex heads to hold the caliper on.
Whether pin or bolt, lubrication of those is necessary for smooth operation. The torque specs on those is 26 ft.lbs.
Torque for banjo bolt is 35 ft.lbs., for caliper bracket is 125 ft.lbs.
The guides on the caliper bracket, for the pads (backing plates) to slide on, build up with rust scale. They should be cleaned up with a good filing, and lubricated so the pads can slide freely on them. The very ends of the pads fit into these guides.
Anti rattle springs, on the Teves system, hook into the caliper. For the TRW system, I don't know, but their purpose is to put some pressure on the backing plates for the pads to keep them from rattling around. The inboard pads will likely have anti rattle springs that push ito the piston cavity.
Sounds like you are using old pads with some anti rattle pieces missing. Any cracks in the pads? Loose pieces of pad (unbonded areas) will cause squeaking.
The contact area where the piston contacts the pad backing plate is where the lube or anti squeak compound is needed.