I have a credit card $500 spending offer where I get $200 back.
1) You mean like a credit card sign up bonus? personally I wouldn't put it in my cheshbon, I spend more than $500 on my credit cards in 3 months, so the $200 I'd treat as extra cash, not as like a giftcard to splurge on something with. So it wouldn't affect my budget for a new laptop and how much I view it as costing. That said, each to their own, and treat it however you'd like.
2) After all that, what's your budget, screen size preference, and what will you use it for? Besides the regular stuff, any photo or video editing?
3) Between the two you sent (not sure if you meant to post three) the one with Ryzen 9 is worth $100 more (Much more powerful processor, usbc/thunderbolt, says 300 nits, larger battery, faster ram, etc) the Ryzen 7 though is much more power efficient, so it might be worth thinking if you need that extra power.
FYI, the specs on the more expensive one say the body is aluminum, though I have no idea what "tough military standard material" means practically. The army has specific standards for ziploc bags, are these laptops made from that material? it's military grade.
But generally speaking, I'd think twice about dropping that much money on a Vivobook, unless you get some firsthand reviews from friends. In my friend group there aren't many viviobooks, of the three, mine died within two years, one is still going after 6 years, and one was destroyed by external forces. (not to be confused with zenbook)
for 7/8 hundred dollars you can get a Gram, Yoga, Envy, etc.
All IMHO