Everyone's process is different so I'd personally reccoment joining a couple of discords and asking around, primarly designers as they always have insightful feedback and a general overarching concept of keycaps and how to run IC's
However, regarding renders I would highly reccomend using this keyboard render it by ImperfectLink. It contains a variety of boards, any customization you'd desire and fairly simple ease of use. It does cost $36 so I can see how that might be pricy however, consider it an investment if you're going to follow through with your designs. There are some other free render kits that are also used on Blender if you're interested in those as well however, as expected, you are losing out on some benefits.
Best of luck and I hope I could help