I, too, have only experienced extreme lag and frustration while using VW 2018.
I learned Vectorworks on 2017 while working for a firm that used iMacs. Now I am on my own and purchased two years ago a license of VW 2018 to use on my 2018 MacBook Pro. I can assure you it has been nothing but painful.
The SP3 update helped alleviate some issues – mainly the freezing software whenever I would edit a text box. However, there is still a very noticeable lag between any command, which includes panning! I'll get a spinning beach ball when I want to adjust the dimensions of a rectangle, which lasts as long as 30 seconds. I wish there was a cure-all fix, but nothing has happened in the past two years. Can someone confirm whether 2019 or 2020 have solved these issues? The last thing I want to do is give up on the program and let my knowledge of VW go by the wayside.