Regular backups only back up changed files by default after the initial full backup. Block-level backups back up changes within files (good for large files like Outlook PST files). With block-level, you need to schedule (as a part of the wizard) periodic full backups of those files backed up using block level. If you don't have many large files that would benefit from block-level backups, then using the standard full + incremental backup of changed files is all you need.

Could you clarify the statement of WillR "When the block level backup does a periodic full backup does it upload all files or only those that have changed since the last full backup (the latter I hope)?"

Only the full files in question. Everything else is still backed up only if changed.

Thank you for your answer. So if I have a block level backup set of 4 files, (files A,B,C, D) and only one file has changed (file C, by example) since last full backup and time comes and next schedule full backup is fired, only file C is uploaded to build the new full backup?
Even more, only changed blocks of file C are uploaded? CMB is syntheticfull backup capable?

Correct. However, synthetic full is a term used for image backups and does not apply to file backup with CloudBerry.