For washing, my poly ties behaved reasonably well in bunches of 10-20 which I would put in a lingerie bag preferably (mesh for lots of water flow), and secondarily in pillow cases. I'd do maybe 5 bags/pillow cases per load?? My normal wash cycle (which then was warm wash and warm rinse) with my usual scent free detergent. I'd throw them in with bits of regular laundry that wasn't picky, jeans, old towels, things like that.
I do a lot of small piece washed in pillow cases -- I use my hair pony tail bands to keep the pillow cases closed. I could tell a lot from the ties that raveled a lot... be prepared with a pair of scissors to separate the ones that didn't play nice. I'd make sure they weren't in a tangled mess and then threw them in the drier, still in their bags again medium heat. I don't use any spray starch or other additives. I was cautious but didn't have any major melting issues and found a lot of those ties could handle pretty high iron heat and a lot of them came out just lovely with no pressing at all. Some of those ravelly ones also needed so steam to press out issues. In good news, once they were washed dried they didn't wrinkle and took a lot of abuse being stored in a garbage bag for years before I gave them away and came out ready for use again.
We had a thread recently about "when was the last time you used pinking shears" -- this was one of those times. I think you might want to do some test batches of what works for you and your project. I was ok gutting them and washing them whole, but if I was to do it again, I'd simply use the pinking shears to cut around the main shape on the front and just ignore the neck and back unless I wanted a lot of 1" finished pieces. I did use the pinking shears where the lining was sewn into the point of the tie. While some of the poly ties were pretty usable at the side creases, the more silky ones typically had a lot of thread damage from the creases that didn't come out.