I and SO have 2 CF cards but never maxed out the quarterly categories

Looking at this thread, I understand that there are three possible avenues to maximize -
- Buy GC's thru Walmart (pay the GC fee BUT can we not buy Walmart GC which has no charge?
- Pay taxes or some other bills in advance (usually a charge between 1.5-2%)
- Use Paypal Key (I read some places that Amex has restricted/closed many accounts using PPK, so Chase may follow?)
Seems I am probably missing some tricks here? Never maximized the quarterly bonus's so trying to start learning this now

Any guidance will be nice, thx
I only recently discovered PPK. Thanks to it, I'll be able to max-out this quarter... which is not always easy given that the wife and I have four* Freedom/Freedom Flex cards between us. That's $6000/quarter category spend. Every quarter. Year in and year out.
*Soon to be five.
RNE, on a UR-hoarding treadmill hell of my own making.
Wow, this is great.. Would not hurt to learn more.
Curious on how PPK is being used