Ok, so for HDFC cards, here is what I have decided:
1. HDFC Infinia (both for primary and secondary cards): Purchase Amex Pay Vouchers for 20k and another 20k for either flipkart or Amazon shopping voucher, as per the requirement. Additionally, using the card for hotel or flight bookings. Total will be around 50-70k per month, depending on requirement.
Also, insurance payments, which are not available through Amazon, to be paid from this card, to get 3.33% returns.
2. HDFC Biz Black: For my Company, generally the monthly tax payments are around 3-4 Lacs but I will use this card only for tax payment for maximum of around 50K for getting 5x benefit and also to ensure that I do not overspend on CC which might attract IT notice!
3. Amex Plat Travel: This will be used alongwith HDFC Infinia for all other spends.
Let me know how it sounds to you !