When to is it best use flexbox and when is it best to use the grid, pros and cons of both and any additional advice, thank you.
By the grid, do you mean something like the Bootstrap grid system, or the as yet unsupported native CSS grid?
At the moment, it is better to use Flex, simply because native grid won’t run reliably on most browsers:
I just realised this is responding to a 2 month old post.
(I dislike the forum software’s habit of invisibly necro-bumping just because someone edits a cataegory tag…)