When I was learning Flexbox, I've created a graphical cheatsheet [1] (based on another one) that I've printed out and put next to my computer. It helped me a lot back then.
That's the most succinct quick reference I've found on this (I've always had trouble digesting the css-tricks article). Have you thought about making a similar cheatsheet for Grid?
I can never keep align-items vs justify-content vs align-content vs justify-items straight and this helps (although it's missing the last one, maybe that only applies to grids).