MY CLOUD HOME slowing PC down

I have just set up the My cloud home and set up a sync as a back up to my PC. The transfer still appears to be syncing after several days/ a week. If i use my pc it is running slow and stalling. There are green sycn icons on some files and ticks on others. What are these icons representing? I assume they represent some files are still syncing and some are done.
My transfer sycn is about 1TB. is it normal to take this long to sync and after the initial sync will the disruption to my desktop improve? in other words will my PC speed up again?

It’s a two way sync, not a one way data transfer.
The following articles will help obtain clarity