Technically, there is no difference between mts,m2t and m2ts files. They're all pretty much .m2ts files. It's like the difference between a .jpg and .jpeg file.

However, not all m2ts files are the same! It depends on the codecs, frame rates and pixel dimensions used to create them.

It's not a good idea to mix video with such drastically different frame rates in the same project. If you do, the program will do its best to blend the frames -- so the results may be acceptable in a pinch.

But you'll get the best results -- and the most efficient performance from your program -- if you match your project specs as closely as possible to your source video specs!