I have MC and had no issues with it. Not sure if visa signature gives any additional benefits.
No spend criteria or no quarterly cap for lounge access. Its 12 lounge access for the whole year. You can use it whenever you want. Add on cards can also utilise the lounge access, but i think only 1 card (primary or add on) can be used at one time.
Card does have 4lac spending criteria for fee waiver, but i got it converted to LTF by dropping HDFC an email.