I have the same issue-using a NAS tho, which is NOT supported by Intuit.  I've used it for over ten years with no noticeable slow down UNTIL the 2018 software.  And it was only with the individual module.

I limped thru tax season using a "tennis shoe" network and kicking employees out of the individual module as necessary (thus totally wasting the money I spent on the 4 seats/Fast Path).

The first article linked is TWO YEARS OLD....and my exact same system worked just fine two years ago.  

So (at least to my way of thinking), something change with the 2018 program.

Now that I've survived the Oct 15th deadline, and all my quarterlies are filed - it's time to figure out what the hell to do.