EVGA product launch are EVGA products no matter where you buy them from. The card has two serial numbers on them, and those serial numbers must be intact and match. There can not be any damage to the PCB, so dropping the card or breaking off components, or even scratching the pcb with a screwdriver while trying to remove parts will void the warranty.
Second hand cards have a slightly different warranty time frame, and many people will sell their cards broken so that other users can “try to warranty” it themselves, which usually means the warranty was already denied or they would never say that themselves.
You do not have to change the pads, and can send the card back with the original pads. Reddit blew the temperatures WAY out of proportion years ago, which ended in EVGA changing the design of the coolers they utilize, and the design change was very beneficial. Thermal pads do not dry out very quickly, and will last a very long time.