When you say "...using VBA 2019 module with AutoCAD2020...", I assume you mean the VBA project file (*.dvb file) created with AutoCAD 2019. *.dvb file created with AutoCAD2019 VBA should work without issue in AutoCAD2020, as long as AutoCAD 2020 has VBA environment set up/installed (i.e. VBA Enabler installed). Now that you have already using your VBA module (your VBA code project?) in AutoCAD 2020, that means VBA environment has ALREADY installed with Acad2020, what else you need to download/install? No, Acad2019 or Acad2020 VBA does not code run slower/faster in one over the other, at least not noticeable.