Hi John,

On Catalina you can use AutoCAD 2019 with 2019.1 Update, AutoCAD 2020 with 2020.1 Update and AutoCAD 2021 OOTB.
Starting from 2018 version AutoCAD saves drawings in 2018 DWG format by default. So if you plan to collaborate with a company that uses 2017 version of AutoCAD, you need to save drawings in 2013 DWG format before sending them to coworkers. You can set default format for save in AutoCAD Preferences.
I'd recommend you to use 2021 version as it contains new features and has less bugs.
If you create only 2D drawings, you can try LT version, but keep in mind that you will not be able to use custom AutoLISP utilities with LT.