Get Chase Sapphire Preferred. Not the Amazon card. 50K points bonus and free annual fee first year. At the least those points are worth $500.00. At the most $1000-1500.00 via various travel etc. Ill bet the $500 in gift cards is more than you get at Amazon (first year @3%) The Amazon card has no real bonus. After year one dump Sapphire Pref and look at some other strong bonus cards.
And Get Citibank Doublecash for 2% on everything after you get the Chase bonus.
I have the card and can confirm, it does not charge interest until the end of the billing cycle. If you pay in full whatever is on the statement you are fine.