I can only speak anecdotally, but I’ve bought dozens of used network/server components and refurb drives off eBay over the past few years and haven’t had a single bad experience. Once a seller forgot to send one of two cables I ordered and immediately shipped the second on their dime. As long as you’re buying from sellers with good feedback you’re likely going to be fine. That said, I can’t speak to their warranty system as I’ve never used it.
Also, if I recall correctly Newegg got bought by some conglomerate a few years back and has apparently started the process of enshitiffication. That’s just something I recall hearing though - I think I’ve only ever shopped with them once, years back.