I recommend you use Shop with Points on Forward (to make it simple, yes it is similar to AMEX MR points), and independent cashback on Chase Amazon (to earn more).
When you use points, you don't earn more points on redemption amount.
Example, you use $20 Chase Amazon reward torwards $100 Amazon purchase. You charge remaining $80 on your card and only earn 3% reward on those $80.
Instead you can charge the entire $100 on the card and use $20 Chase Amazon reward as a statement credit. You still end up paying $80 but now you earn 3% on $100.
