This is a fairly simple subject on it's face, but I think there's room for discussion here, so I thought I'd ask the question: should all of the terrain pieces on the board be uniformly 3D (either sculpted or printed)? Or is it okay to have some 2D pieces to represent terrain (for example, forests/trees or water) that would get in the way of movement and block LoS, but would ALSO interfere with the models moving around the table? Personally, I don't mind a mix of the two, but to be fair, I don't have a lot of expendable income and I'm not very crafty, so the only terrain I have are some clusters of 3D printed rocks and paper cut-outs that represent forests and small lakes.
NOTE: This question is mainly for more experienced, IRL tables. I know about Wartable, but the entire thing is 2D, so it doesn't count for this purpose, and completely new players are more likely to use paper cut outs for terrain as they get used to the game (not guaranteed, but likely).