If a new version of a particular block has been released, you'll see an Block Update Available notification at the bottom of your block settings sidebar (as shown below). Using this functionality, you can update your block to its latest version with a single click, preserving all the stylings and configurations.
Click View details to see the update changelog and make the update.
Note that there might be cases (of which you'll be notified in block settings) when the Update Block option won't be available and you'll need to remove the block and add it again, redoing the block setup.
Any block you add in your Softr app after the release of the Block Update feature will be assigned a 2.0.0 version and will start supporting the one-click update functionality. Blocks with older versions will still need to be updated manually (removed and added/configured again).