Peelable paper leaves the paper backing that ready absorbs water, strippable paper must be scored to allow penetration past its water resistant surface. A tool called a Paper Tiger has spurs on it to prick the paper and provide these points of entry. You are lucky to live in the last part of the 20th century because there are lots of different methods to choose from for wetting the glue. Newer methods include a semipaste gel from DIF that clings to vertical surfaces and also newly marketed is a sheet of absorbant material that clings to the wall and soaks the paper. Different people have different preferences.
Most people use the liquid strippers.
They cost the least but are the most messy as they run down the wall. Steamers have been around a long time but are rather unpopular. They have a container that connects via hose to a plate measuring about 1 foot square where the steam comes out. This plate must be held against the wall until the surface is soft enough to clean. I don't think people use them unless other methods fail.