I’ve use PW before and it’s not too bad. The API is really great and so much nicer than working with WP custom fields (etc). The only downside was the back office... a bit dated (looks like something from 2009). The way the CMS works and the thinking behind it are great though.
Grav is cool, if you need PHP you’re good with flat file.
Off topic, but my most fav CMS of all time is definitely Umbraco. It’s built on .NET, but it’s insanely fun to work on.
Between all three if these CMSes, I cringe when I hear “Wordpress.”
It separates the CMS from the front-end and has a very good API to get the data from the CMS.