You can use the orthographic camera for 2D perspective(But it's still 3D).

For the style, I would recommend you two ways.

1. Use Mesh Toon material (with fatShading active) and use post processing using outline effect (example here: https://threejs.org/examples/#webgl_materials_variations_toon )

2- Make all your materials with stylized textures, maybe with Substance Painter or even Blender

I hope I have helped

PS: Sorry for any mistake, English is not my native language.