You can disclose the source per unit (personal upgrade / studio decommission / etc.). If you do not sell ex-mining cards, state that clearly. Always be truthful and keep test notes.

Add per-item details like suggested PSU wattage, power connectors, and card length. Buyers can share CPU/PSU/case constraints for a quick check.

Yes. Book a time and agree on what to test (game/benchmark/render) to avoid setup delays.

Yes. Mark items as “Reserved” and specify the hold period and rules.