We use fitteds with fleece pants (longies) during the day- no separate cover. This is the trimmest way to use fleece, ime. This is my fave. We change at every pee. You do need decently absorbant diapers if you don't want leaks down the leg, or wicking through the fleece.
For outings, we use pocket diapers- we've not had a leak in a pocket diaper in a very long time. I think we just had to figure out what we liked, and we out the rest. We use pockets if we have company that might hold ds. We usually don't get wet with the fitted/longies combo, but our fitteds are thin, and if he has a big pee, you can feel the dampness through the fleece. Doesn't bother me (you don't actually get wet), but it might bother others.
For nights we use a "trifolded" flat laid in either a pul cover or a Swaddlebees fleece cover. The swaddlebees cover is quite trim for fleece, but I don't think it would stay on securely very well during the day. I could be wrong, though.
eta- you can use any thick fleece pants as covers. They have to be 100% polyester. I find that sometimes the elastic band gets damp if you don't use absorbent enough diapers. For that reason, I prefer WAHM longies, but I have lots of Old Navy type fleece pants that work well.
Becky, partner to Teague, SAHM to Keagan (7yo), Jonah (2yo)