quickest way to find serp features opportunities?

Don't spend time on FAQ schema for this. Since 2023 Google only shows FAQ rich results for a small set of well-known government and health sites, so for most of us it shows nothing. HowTo rich results went the same year.

Order that has worked for me: pull the queries where you are already in the top ten, look at what those actual results pages show, and work only on the features that are present there. Featured snippets first, because those are nearly always taken from a page already on page one, so you are editing rather than starting over. Images and video next if the SERP shows them. Chasing a feature on a query you rank fortieth for is where the time goes.