Thank you,

You are correct that i create my vector designs in AI. That is really all i need.

But because my vendor A raised an issue saying the scaling was dramatically off (by a factor of a few thousand percent), i decided to subscribe to AutoCAD 2018 in order to try saving it within there and send them that. I believe that worked, so something must be different from the AI export vs the AutoCAD file saved. Both DXF. 

One thing I'd like to point out is this.. when i export the DXF from AI, and open it in AutoCAD, it automatically displays as jagged lines in AutoCAD. This happened when i very first ever used AutoCAD a couple weeks ago. I simply downloaded the software and open the DXF and all of my curves had jagged lines. 

However, I had not made any adjustments to the export process from AI, and there really aren't many options either. This is AI 2018, completely up to date. 

Here are images of the Vendor B process, in order of the process. This is the vendor that is saying i have "splined/jagged" curves. Please continue to read downwards..

First is the drawing in AI. Perfect curves of course.

Then is the DXF export window, with the default settings. The scaling window is covered up, but it's just 1 to 1. My issue isn't scaling with this one.

After that is opening the DXF is AutoCAD 2018. You can see if you look closely that there are jagged edges. 

Then after that is a zoomed in close up of jagged edges.

Then last  is the window with adjustments for documents settings, which i have been trying to understand but sometimes i don't see any results whatsoever. However, I am assuming from what you said that these have no affect on the document itself as it's imported, exported, or saved. The only reason i ever tried making adjustments in that window is because AutoCAD, from the very first moment, made curves appear jagged. Again, i have never used AutoCAD and/or opened any documents ever before this. So it's confusing as to why the default settings for AutoCAD would be set so that curves were jagged. Additionally, i have made no other settings adjustments in AutoCAD.