Initially I wasn't ready to merge all answers from this question:
And move them to this question:
I think it's best to keep them separate since one is High Sierra and deals with Apple reasons for the delay. The other deals with third party reasons. Also - both questions would need an edit.
If we end up with 5 or so linked questions - we can revisit if making a clean "canonical" question to hold all the answers is best - but at this point the close as duplicate seems to serve all interests well. I have bounced this across the moderation team in our chat window and the consensus today is to not merge the two posts you flagged.
The best outcome I can see would be to have someone, perhaps you Kevin ask the fundamental question - "How can I use fs_usage or another tool to measure and diagnose a delay of 10 seconds adding a file to the desktop of Mac OS?" That question could be narrowly framed - link to all the questions (merged or closed or open) that exist and then have an answer explaining how to measure the activity that lets anyone know which of the dozens of sync services is throttling IO.