Properly engineered 2-ways generally exhibit wide, well balanced response in the horizontal plane, but often some noticeable irregularities in the vertical plane, due to the ways frequencies shared by both drivers tend to interact in the crossover band. For a vertically aligned speaker, the tweeter height is not the real issue, it’s finding the sweet spot where the midrange is not “sucked out” by phase cancellation, and a combo of height and toe-in is usually successful. Rotating to horizontal makes the likelihood of achieving this result far less. I suggest using “coincident” 2-ways if you must do this. KEF, Tannoy, and Elac are known for this and more recently MoFi. Andrew Jones is a big name in this field.