When a room becomes cluttered, it's easier to clean up by seperating the items into different piles. The same is true for your gigs. Seperate them into specific categories and you'll be more likely to attract the buyers you want.
I think in terms of category, you may be fine, but your service type could be more accurate. "3D modeling and rendering" is a pretty broad term that could encompass anything from simple 3D models to full product renderings. If you're only getting requests for CAD modelers, it's likely because your gig title and/or description aren't accurately reflecting what you do.
You should seperate your gig into multiple services, each with it's own specific title and description. That way, buyers can more easily find the services they're looking for. For example, you could have one gig titled "3D Modeling" with a description that outlines the types of modeling you do, another gig titled "3D Rendering" with a description that outlines the types of rendering you do, etc.
It isn't necessary to have a gig for every single service you offer, but the more specific and accurate your gig titles and descriptions are, the easier it will be for buyers to find you.