I've tried lowering the quality of the plot in CAD but that makes the curves so bad it's unusable. Every time I try and open the exported file in Illustrator it takes forever and if/when it loads if I click anywhere on the screen it takes forever to process. Each edit on the document takes 20 to 30 minutes at least.
Hard to assess anything useful to answer in specific detail - but I'll give some general thoughts:
1) Illustrator happily reads in
.dxf natively, though with some caveats (e.g. explode blocks, explode fill patterns) and being Illustrator, not CAD, there will be scale issues.
2) Illustrator natively reads
.ai variant; this is my preferred method of "bringing in CAD" about 85% of the time.
Assuming you experiment and end up, as I do, preferring
If the "work" being done in Illustrator is basically colour-up, then keep the CAD linework on a wholly separate layer set, and do the colouring work beneath it. If you need to edit elements from the original CAD, then isolate JUST the stuff you need and drag it to a new layer, and work on just that on its own.
As @user287001 said in their comments, fills are often the unguessed-at culprit for CAD-started Illustrator files which drag, glitch and generally suck - it's one reason I tend to try to keep those CAD fills on a separate layer in the
.ai file so I can turn the darn things off to work if needed, and in many cases I end up simply re-drawing the fills as native Illustrator patterns - you almost always get way cleaner output for far less trouble.
I wouldn't lower your curve resolution a ton, I don't generally find that helps a lot - I'd guess your struggle is fill related. Moreover, if your curves end up looking lousy, re-draw 'em in Illustrator with the Arc tool or with béziers.
Hope this helps - you are helping me remember that I do not miss AutoCad at all.