Hi Dee!
That Paula’s Choice product sounds like a really nice multi-acid blend.
For how often, the manufacturer says once a week and that’s a fine starting point.

But honestly, it helps to just see how your skin responds first before locking into a schedule. If your skin is calm with no lingering redness or sensitivity between peels, once a week is usually fine. If not, space them out. Some weeks I do a peel, some weeks I skip it.

As for the 20% glycolic – once you’ve been doing the Paula’s Choice peel for a while and your skin is handling it well, that’s a good time to try it. I’ve always been able to do a 20% glycolic once a week without any issues, and to me 20% isn’t too strong, but it just takes time for the skin to acclimate and everyone is different. Maybe try it every 2-3 weeks at first and see how you do.
And always wear sunscreen daily when you’re peeling. I hope that helps!