Talked with my Pinterest Ads rep today and got some more insight on a couple commerce features in beta.

ROAS Bidding
This is a tweak to Performance+ bidding to focus on conversion value, adjusting the bid based on the expected return.

It works best for those with a wide spread of price points. And, as always with algorithmic features, requires consistent signal of decent volume (current benchmark is 30 conversions a week).

Promotions
Mentioned this in the October platform updates roundup, but now have some more info.

It adds promos / offers to ads in campaigns geared to on-site actions using a selection of template options across 3 categories: discount, shipping, and conditional (spend $x, get $y off, etc).

Shopify integration available, including automatically applying promo codes at checkout. Not sure how it functions without Shopify, guessing there will be a Promotions section in the catalog area where you can manually add a template.

Bonus Best Practice
Pause ads that have been running for ~2 weeks with low/0% CTR and replace with a new one. The inflection point CTR is somewhere around 1% , I think.