Yep, trial and error really is the best way, cos you don't know what'll work best, plus what one person likes, another may not.
The classifieds on here is a good place to buy preloved, but there are other sites too, just keep your eyes peeled!
I changed my dd a bit more often that 5 times a day, but again, it depends on the child! Regardless of nappy type, I don't like the idea of them sitting in pee for longer than 2 hours ish, so would work to that in general, meaning I'd probably need 8 per day max, plus a night nappy. I air dried on clothes horses, and with a nappy load every second day, this gave them 2 days to dry which was plenty. But I had a huge stash, so this was never a problem!
As for bulk, I can't really help, cos to me cloth bottoms are normal and disposable bottoms are weirdly thin! If she was wearing close fitting trousers I'd go for an itti I guess, but generally I worked clothes around nappies rather than the other way. Possibly easier with a girl though!
Pocket nappies, all in ones and 'all in 2s' like the itti d'lish don't need a separate wrap as they basically build it onto the nappy - the pocket is a sandwich of waterproof outer filled with absorbency and the other side is the liner. Similar logic with AIOs and AI2s. 'Fitted nappies' are like shaped terry or velour or other absorbant fabric, and to be waterproof they need a separate wrap on top. Typically the wrap can be used a few times. A bit like your snap in ones, except both the wrap and the nappy will have poppers or aplix to fasten on. They're really good for absorbancy and poo containment for newborns. You can also use wool on top of fitteds instead of a wrap, which is a whole other addiction!
Hope that all makes sense!