Some general pointers:

- Applying separately as a principal may be beneficial when there are good sign up promos (i.e. free stuff). Also, free airport lounge access is PER PRINCIPAL (i.e. 3 free lounge entries is combined for principals + subs). So if you intend to use the lounge more than 3 times per year, worth considering this point.

- If the above does not matter to you, then applying as a supp is a good option provided you opt for separate statements (tick the correct box in the application form). This will enable each supp to its own 6% cashback (subject to RM50 monthly limit). If you read the past few posts, some supps have had difficulty applying for online banking (and online statements) where they don't have CASAs. I remember reading that there is a solution to this, but I have not personally tried it so cannot comment further.

- Having a principal + several supps may help you with achieving the eligible spend for PBB's many promos. Based on previous experience, there have been several promos based on "swipe RMXX for XX times per week and win RMXX on first come first served basis". For example, the current promo is swipe RM60 5 times (RM20 cash back) or 10 times (RM50 cash back). Achieving the requisite number of swipes alone as a principal may be difficult. So your supps can help you. However, promo cashback will only be credited to the principal account.