First off, dont be overwhelmed at all. I think cloth is a lot more info than it is work.
If you're stuffing an insert in your Alvas and Charlies than theyre pockets. If you wanna take a pic of them and send them to me just to confirm feel free. So inserts = pockets UNLESS you have a PUL shell or cover and youre snapping them in. That makes them AI2s. I wouldnt worry a crazy amount about the differences right now.
I think when you refer to PUL liners youre talking about PUL covers which are the plastic type things you snap an insert into, lay an insert in, or put over a fitted. Aka the things that make cloth waterproof
Since you already have the disposable inserts I would use them at first because itll make things a little easier for you but its been in my experience that a lot of babies are done with the meconium stage by the time they come home from the hospital, the exception being home births. As far as diapers go in the hospitals, def dont feel bad about using the disposables they provide for you. First off they're free. 2nd, we were advised not to bring things back and forth from the hospital and to keep the things we brought there at a minimum.
I'm def a fan of buying used for many reasons. But just because you're told to expect a baby doesnt mean you will have one. My daughter was measuring around the same as yours at 33 weeks, at 38 weeks she measured over 8 and was born at 7 on her scheduled c section date at 39 weeks. Sonos are usually off by 1/2-1lb in either direction but can be more. When I brought my daughter home she was 6lbs 7oz and I regretting not buying anything for the newborn stage. None of my one size diapers actually fit until 10+lbs. Point being you could give birth to a 7 pounder or a 12 pounder but if you bought some newborn prefolds and covers used the only prep youd have to do would be a bleach wash (must be done on anything you buy used). If your baby ends up being 10lbs then go right into the small size. You can turn around and sell those newborn covers and prefolds and make back exactly what you spent. Also if you end up using them for a couple weeks and theyre still in the same condition you bought them in you can also sell them for exactly what you bought them for.
Dont underestimate the small size prefolds. I still use them on my 12 month old who is 22lbs. I started out with folds like the angel wing and bikini twist. Then around 3 months old I started using my pockets more and from around 5 months on I pretty much only used trifolded prefolds. As far as prefolds go you might want to buy a "wider" prefold for the time period which you're going to be wrapping it on your baby. The brand Imagine makes wide ones called "smart fit" (Or "better fit" - i forget) that were great and fit longer for doing the angel wing. A lot of brands including GMD offer wide prefolds but Imagine is the only one I have personal experience with. But I prefer my regular old small GMD prefolds for trifolding because I dont have to fold them down in my covers.
I would still to small prefolds at first. If you do get newborn stuff you can always sell that and put it towards buying medium ones.
covers- you will not get away with using 1 cover per day. You need minimum 2. You alternate between covers (hanging the used one to dry) unless poop gets on the fabric parts of the cover then you put it in the wash. If poop gets on the plastic part of the cover you can just wipe that off.
fleece liners are not disposable. You wash them with your regular diaper laundry. Disposable liners are "flushable" (I did a PSA a while back, i dont recommend flushing them) but they look sort of like dryer sheets. Pee goes through them and gets soaked into the cloth and poop stays on them. The function of the fleece ones are to a) work the same way as the disposable ones if youre cleaning poop off your diaps and b) to help wick moisture away from baby. You dont need them with pockets or AIOs because they should already either have fleece or suedecloth.
A lot of people tie dye their prefolds. Just make sure you get all of the color out before using them and keep in mind that you may get less $ back when re-selling.
If you have any more questions about anything feel free to PM me anytime.