For 2.5" drive bay fixed in 8SC48 chassis, I see that the website information is telling me;
MCP-220-00044-0N (MCP-220-00048-0N needed). Which of those 2 i brackets need to get 2x 2.5" fixed drives in this chassis?
You need them both. The MCP-220-00044-0N is the backplate that you mount to the chassis, and MCP-220-00048-0N is the 2.5" bracket that holds the disk and is mounted to MCP-220-00044-0N