Too Long; Didn't Read
Both Flexbox and CSS Grid are tools to make the layout of your page better so that it looks amazing. Using them is simple and allows you to control the way your page looks easily. Both have similar functions to do certain things on your pages such as justifying content and vertical alignment but at the same time, they do some other things differently like what's in the next segment. The best thing you can do is use both as you need them by section. Use all of the resources they offer and make an amazing page using Flexbox.