Your plan is good, VN, then 3d, but, depending on the time you are ready to spend, you can do both, as they are quite different.
As for realism, you probably already know, but use big textures for your characters, including normals/bumps, also if you use backgrounds/hdris or rooms/buildings/props/etc, make sure they have big textures too (in particular for closer renders). After that it's the lighting, but the final step is the editing in photoshop/gimp/etc. Playing with levels/hue saturation/highlights/filters(noise/sharpen/etc) can add to the realism.
I don't know if there is a magic formula, as the post-work depends on the render, but a render alone is not enought to achieve the "best" realism imo, unless you spend a Long long time tweaking your scene, and it would be considerably more time compared to rendering and editing in photoshop/gimp/etc.
One of my favorite lighting assets is :
https://f95zone.to/threads/summer-light-for-iray.14290/
It's a simple two light sources asset, but it got me started (the Light F in particular I still use alot, with some editing), and it is realy great for outdoor scenes. You can tweak the light sources, analyse them, select them as your View and move them, see the effect, etc.
Also, there are some assets that can help with fog if that was your goal, such as:
https://f95zone.to/threads/iray-distance-fog.34925/
And there are many others.
I like your render, it is Realy good imo, just a bit too whitewashed for my taste as
-L-L-MJ- said, but playing with the levels in photoshop can increase the constrast, and running it through the nvidia/intel denoiser can counter the noise. (
https://f95zone.to/threads/nvidia-ai-denoiser-2-4.35677/)
I tried to attach a short video (23meg) showing what I did to get this result from your render but it said it was too big, so I put it on my youtube on link only.
Back to the subject thou, it is up to you what result you want to achieve, this is just my personal take on your render, which is already pretty good (your render that is)! A little too green, but I didn't mess with the hue, I did what the video shows, so playing with the hue can give different results, warmer/colder colors, etc. The main point is that it can all be done in post-work, and it saves rendering time.