What determines choice of law or tax paper variant

Good day sirs

I am a bit confused about the choice of law variant paper that i should opt for in the F4 exam entry.I just got my FIA Diploma this month and have been transferred to the ACCA register.They automatically opted me for English law variant and Global tax variant but am sure there is an option to change that according to your preferences.My question is what really determines the choice of variant paper.It’s confusing me because i am currently living and studying in South Africa,so am not sure which variant is best for me, the one for my own country or the one for South Africa or where does the global variant apply?Thank you