What motherboard suits Core 9 273PE, and how should power delivery, memory, and ports be balanced?

  The 273PE is an engineering SKU — the name doesn't reveal the socket, chipset, or DDR4/DDR5. Verify the exact SKU, socket, chipset, memory type, and minimum BIOS in both the CPU and board support lists.

  Only if the list explicitly says LGA1851/800-series/DDR5 should you choose B860 for stock or Z890 for expansion; otherwise, buy a board that explicitly lists this SKU.