Weird how many people have mold issues. Never seen a moldy album. But have see a ton of dirty, scratched and nasty album covers. Think if mold is an issue you should have desiccant around your collection!!!
Not sure if they use it anymore, but the old plastic that albums used to come with can leach onto the album. I was told to always remove the plastic they come in. Just paper, or cardboard sleeve just scratch and imbed stuff on the records. So don't use them either.
All my records have proper inner and outer sleeves. Have tried a few places, but MoFi makes great ones, as does Vinyl Storage Solutions. Anytime there is a sale, I just stock up, usually getting a few hundred at a time. Have a bit over 3000 records.
It does help keep them clean, easy to slide in and out, keeps the jackets pristine. When storing records, I put the outer sleeve pointing up, this allows you to slide the album in and out of the rack without the sleeve coming off, or jamming. Also put the sleeved record in the back of the album jacket on the outside, but inside the outer sleeve. Albums never fall out, are very easy to remove for play. It also allows me to never have to remove the sleeves, will never damage the record jacket, trying to get the record in or out of it.