WAR chip is only useful if you want a custom tune for your car. Want to try tuning your car yourself. Or want to have different tunes for different occasions.

No need to go all out with the WAR + MAF combo. The MAF kit comes with a tune for your car. It's a little over $300 to get just the MAF kit (not bad considering just a new MAF for my M-Sport is that price on average).

I'm not sure how running a bad AFM works. For bad MAF's you'll get a rough idle, bad gas mileage, and eventually I think it won't run. But the AFM is a mechanical unit while the MAF is not. And I don't know if the flap in the AFM will still open when it goes bad, or if it just misreads and has slow response when it goes bad.