well if u want something like spirited away or howls moving castle, the guy who made them Hayao Miyasakis movies would be the place to start.
Since u liked cowboy bebop I am also inclined to suggest baccano since Its also around the same style but is about mafias who gain immortality with a really good plot.
If u do plan to go for something a long spirited away or howls moving castle route I would suggest Princess mononoke since its one of my personal favourites from their creator and I think you might enjoy it.
I don't really have anything old in terms of something similar to Ghost in the shell, but Psycho pass comes close with it also being a futuristic police show bare in mind it would have CGI animation and not old hand drawn or traditional methods still worth a watch.
Other things to check out on a whim are Mikoto shinkai films such as 5 Centimetres per second. These films are strictly about human interactions and are usually romance based but take a reality check to the face and punch u hard in the feels while keeping a traditional animation style while implementing some 3D animation that blends well to add some real nice depth. You may like it you never know.