I really hated how these 3D objects didn't fit into the style of Paper Mario in the 3DS version.
For the Wii U version I wonder if they actually reward doing the battles, the paint meter already sounds like an improvement in that area. In the 3DS game I just tried to walk past enemies as the battles were so boring. The main issue of the 3DS game wasn't that it was bad, it was just boring.
They do. In addition to experience to level up your paint meters, it's also the only way to get enemy stickers for combat.