Is there a particular service pack we should avoid? I had some issues with smart mates when I went to 2017 sp 5.0, the smart mates had a real bad bug that caused me to go back to sp 2.0. And I'm still dealing with the remnants of the real bad bug that came out in 2016 https://forum.solidworks.com/message/573923#comment-573923 that causes routes to lose dimensions & relations, has that been fixed?.
Install 2018 and test it on one computer first.
I have 2016 and 2018 on mine.
I was using 2016 and have 2018 setup and change file locations in option so they use their own template and toolbox.
Tested 2018 for a week then stop using 2016.