It might work well to do lots, especially if you have some by the same author or similar genre. That kind of thing often sells faster than individual books. When I want to start a series, the first thing I do is go to Ebay and see if someone has the whole set or most of a set for sale.

I would do lots for anything that makes sense to do like that.

If you have signed or first editions, I would list them individually and just make yours the lowest priced. If the cheapest one is $15.99, make yours $14.99. You will still come out further ahead than selling at a local book store. Just be sure you are adequately estimating shipping.

If you want to sell faster and are willing to take more of a loss, take some photos of the whole collection and post a whole collection price on Facebook marketplace or something similar for local pickup. You might do alright. Local sales have always been mixed for me, but, I've done alright on larger lots. It has to be worth the effort to drive and meet someone.