I wouldn't describe most of touhou as 'weird", it's very flamboyant but ZUN's song structures tend to be very typical. 4/4, basic keys, standard verse - chorus style arrangement, heavy focus on melody. part of the reason there are such a ridiculous number of touhou remixes out there, it's easier to arrange something like that compared to something more abstract. it just tends to catch people off guard because a lot of it is fast, features unusual instrumentation, and has a lot of flourishes but at it's core most touhou music has more in common with uematsu or mitsuda than anyone actually weird(akira yamaoka being the first game composer to come to mind...)