I recently had to figure out a good chunk of this (on my own, I wish I had this resource then) for a one-off project. The biggest thing I learned was to give up all hope of cross-browser printing: just use Chrome. Every browser treats almost every property differently or flat out ignores them, but I found that Chrome had the highest score in doing what I wanted.
There are two sites that share a common history that provide a tool for TTRPG players to create homebrew documents, GM Binder and Homebrewery, that both only target Chrome for this reason. It’s great if we can support all browsers and don’t want the site to break in any browser, but we advise users that Chrome is the target almost just so we know authors and readers are on the same page.
The area chrome has consistently failed horribly for me in is in tables spanning multiple pages. Firefox and the old IE engine were far more reliable at this. Chrome has improved a little in this regard lately, but will still routinely spill thead on top of tbody content when there is a page split.
