Posts and Pages can now be previewed on mobile devices with WordPress 5.5. Before Publish or Update button, you can switch your dashboard view from desktop to tablet or phone screen sizes by clicking the Preview button at the top of a page or post.
Basically all the blocks are mobile responsive. There is no additional styling is required for it. But it all depends upon the section you the block. Like if you have columns block with 3 column then it will be automatically adjusted to 3 rows in mobile.
similarly other blocks are also auto adjusted to fit in mobile. You need to keep learning and trying different approach of blocks to master in it.