can i do music and pe Watch
Lots of schools put music and pe in the same group at GCSE so you wouldn't be able to choose both, but there are no rules which say you can't do both
There is no reason you couldn't do A levels in music and pe but they both require a lot of coursework so take a lot of commitment. You have to be able to play an instrument at at least grade 6/7 level and do a lot of practicing, and pe requires a lot of playing sport, so they would take up a lot of time
BTECs and A levels/GCSEs are different, rather than one being easier than the other. BTECs have less exams and more course work. The music BTEC is more suited to pop music rather than classical. They come at different levels (so level 2 is GCSE standard and level 3 is A level standard) and different sizes (e.g. an extended diploma at level 3 is equivalent to 3 A levels, but you can do ones equivalent to 1 or 2.) So if you do BTEC at level 3 you might only study an extended diploma in one subject, or you could do a smaller level 3 course in both, but only if the school / college can timetable both. Some schools offer a few BTECS alongside GCSEs.