Hello! I only read the original post and the first few responses, running short on time, I apologize for any repeated advice.
For the cage... out of the 2 mentioned options, Kaytee is much preferred because it's bigger. However, I'd do away with these cages totally and go with a C&C. I know you're not one for DIY, but it's so easy and you can buy it already made. It's SO much cheaper than the store bought stuff, yet so much better, and you have far more flexibility. I made my whole cage for about $50. And the flexibility was nice. I made my cage a 2x3 split-level for my 2 sows when they were babies, and made it much bigger when they were older and I had the ability to rearrange my room. It's so easy to make as well. There are so many tutorials on YouTube, as well as probably some good info here (haven't looked, but it's probably here). Basically, C&C stands for Cubes and Coroplast. "Cubes" is the office grids you just pop together in the shape you want the cage. I recommend using the feet provided and zip-ties for reinforcement. Coloplast is a little harder, you have to cut, shape, tape, but it's not very hard and there's plenty of tutorials online. You know my vote, if I get one, is C&C, and I can help you with that more if you'd like, but it's up to you. Definitely the Kaytee one over the Midwest, however.
For the bedding... I'd say gather your old towels and buy some Joanne Fabrics. But your not one for DIY. You could sew it together if you cared to have neat bedding, like I did, but people have successfully just kept them separated and layered them on. I've also heard great things about GuineaDad. You dont have to opt for a cage-specific type of fleece. Thank you for choosing fleece. It's definitely the best one in my book.
To answer your question about what needs covered and sizing... put simply... cover everything plus some! It is a huge pain to scrub dried urine from the crevices. Plus, they like the fleece better than the hard scratchy cage bottom on their unpadded feet. Please cover everything. I know from experience. It will shrink in the wash. It will be a pain trying to stretch it out. Also, if they pee near the edges of the cage, it will get on the walls too. It's FAR better to have a bit of fleece come up over the cagesides than to have cagebottom uncovered. It's not a matter of what's best for the pigs, but for you and cleanliness in the long run. I'm sorry if I sounded rude or pushy, not the intent at all, I've just been there and don't want you to have to buy new fleece or dread cage cleaning like I did for months.
TLDR: it's a smelly mess if you don't cover the entire cage bottom, it's okay if there is excess fleece coming up on the side.
Pellets: I recommend Oxbow... you can get them on Amazon, they are good quality, they come in all sizes of bags (if you have the space for a huge bag like I do, it's really nice, but you could opt for smaller)
Vitamin C: Oxbow tablets. Also fantastic, also delicious (for the pigs, I think?), also on Amazon.
Hay: Small Pet Select, for sure. Amazing quality. Very highly reccomend. Come in large boxes. Also, can buy on Amazon. Subscribe and save highly reccomend.
Toys and Hides: fleece pockets, fleece beds, fleece tunnels, chew toys... lots of Amazoned stuff. Lots of good stuff. Lots of options. Just... PLEASE no balls or wheels. It WILL break their very fragile backs.
I think I covered most of it. Please let me know if you have any questions, and be aware that any rudeness was miscommunication over text and not intended. I hope I was some help
