Hello Ellen,
There are four different kinds of pilgrim albergues on the Camino. Those run by the church (mostly 'dovativo - for a donation); those run by the municipality; some run by confraternities or other organisations (Confraternity of St James, Order of Malta etc) - these are also usually donativo; and then there are a large number of albergues run by private individuals. Some of the private albergues are not-for-profit as such whilst others are commercial enterprises.
The private albergues are not necessarily more up-market than the church albergues. Some are very rustic.
The donativo, church, confraternity run etc usually don't accept backpacks delivered by transport and you can't book rooms ahead. (If the volunteers only arrive there in the afternoon there would be nobody to accept the packs anyway.)
The majority of private albergues can be booked ahead and they have no problem with backpacks arriving by transport. You can download a brochure with a full list of private albergues on this website:
http://www.redalberguessantiago.com/ind ... Itemid=268
The Spanish Credencial is a small - 15cm X 8cm - printed card folded concertina style.