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

  The 273PQE is an engineering part — the name can't reliably identify socket, chipset, or memory type; rely on the official support lists.

  Only if explicitly listed as LGA1851/800-series/DDR5 should you use B860 for stock or Z890 for expansion/tuning; otherwise buy a board that lists the SKU and size VRM cooling for a 24-thread sustained load. A gaming build spends on GPU and storage first, adding power headroom only for long rendering.