BTECs do now have an exam but it is not too onerous. It is similar in that there is theory and practical- but the folder and the exam are the only means of assessment whereas in GCSE you are assessed on 4 sports. As long as he does no more than 2 BTECs he will be fine and it will be less pressure when it comes to the end of year 11.
At ds's school you can only do GCSE PE if you represent the school at A or B team level in at least 2 sports (it's a v sporty school so their B team is many schools' A team standard). So many of the marks depend on the practical assessments that unless you are very sporty you're not going to get an A or A*