I prefer the hard carriers: in my opinion they are sturdier and the cat is not going to get out of it. My carriers stay out, they are in a corner of the dinning room - one, because they eat in their carriers and two, because in an emergency I want to be able to get to them in a hurry. You can teach any cat to load into a carrier. The key to teaching them to load, or anything you want to teach them, is to take what the kitty perceives as a bad experience and turn it into a good experience. First put two clean soft towels and toys in the carrier. These should always stay in the carrier. Next you need to start feeding the kitty in the carrier. Mine are fed on a schedule and eat in their carriers, so when I open the door they run right in. At first, leave the door open while they eat. Do this until your cat walks in calmly and walks out calmly. Then shut the door while they eat, but watch carefully and when they are done eating open the door and let them out. Do this for a week or so, maybe 10 days. Mine actually caught on in a few days, but each cat is different. Kitty soon learns that they are not in there for life, that the door does open, and they do come out. Then each day, after they finish eating, leave them in for a minute or so, and gradually increase it a min, every day. Whatever your normal travel time is to the vet, work up to leaving them in the carrier for that length of time. Training them to eat in their carriers also serves another purpose: you can get them loaded and out of the house in an emergency. I once was staying in a hotel when the fire alarm sounded. I had two terrified kittens running around the hotel room, then under the bed, etc. I started to panic about how I would get them out of there. Then it dawned on me: I opened their carrier door. It makes a squeaking sound and they both ran in the carrier. I was so grateful that I had taught them to load.

Speaking from experience, if you have been letting your cat out, he's not going to be crazy about a crate. He'll probably howl and claw to get out. He may be spraying because the former residents had a cat who marked and he's picked up the scent. If he goes out, he may go looking for your old house, so I'd keep him in or he may not come back. Try getting some interesting things to make this house seem like home--some catnip if he likes that or if you can afford it, a cat tree for him. Spend extra time with him because he's probably confused about whether this is a permanent home. He needs extra attention and love right now, even if you are busy unpacking. He's just at a loss and trying his best to cope.