GTX 940MX with 4GB SDR5 and autocad 2018
Yes that graphics card should be fine for AutoCAD.
The rest of the spec is great. I just don’t have experience with that graphics card but I know it’s powerful.
You asked whether it would run ‘smoothly’ with your setup, just bear in mind that it will depend on the complexity of your drawings. You can quite easily slow-down any system with suitable drawing complexity.
I’d love to know how you get on!