How much data is transferred? Will my data allowance be eaten up quickly?
Merlin Server is by far the most efficient method as it only transfers the actual changes. File-based cloud services transfer entire files every time they are synchronized, which naturally eats up more of your data allowance. The cloud services we are familiar with, analyze which sections of a file have actually changed and only transfer those parts, keeping additional consumption in macOS within limits.
Merlin Project on iOS however does need to transfer each time entire files due to restrictions with the interfaces published by the cloud services. This is why MagicSync throttles the upload speed of changes from Merlin Project on iOS; it consolidates as many changes as possible into one upload as in most cases it doesn’t matter whether changes arrive immediately or with a few minutes’ delay. That said, if changes are urgent you can force Merlin Project on iOS to upload changes immediately.