I have some query on uses of customer migration FBDI - Simplified VS Bulk load FBDI

Summary:

I have some query on uses of customer migration FBDI - Simplified VS Bulk load FBDI

Content (please ensure you mask any confidential information):

1. Which FBDI we should used - Simplified one with 4 sheet( customer, Reverence Account, contact, customer bank account. 
2. What is the maximum count can I used to load for both the FBDI? 
3. Also, as per client requirement, we need update option to be used may be after 3 month like 1st enabling 2 DFF & after the 3 month can go for more 5 DFF in the same existing loaded customer master in Fusion. how can achieve this & which FBDI we should used for this update in existing master.