Just go hi-res
You don’t need anything complicated for it to look good. Path tracers like Cycles look pretty dope in with just a random blob in a room.
But the high-end look quickly dies when your assets are low-res. The render above has a 16K HDRI, 4K textures, caustics, bevels, many bounces, and is saved as a 4K png.
The render below has all of that downscaled.
So fidelity matters quite a bit. (It’s more obvious in full screen) Add new elements mindfully, and try not to allow in too many low-res assets.
Now just to plug my product, here is that same render with my compositor preset turned off.
Inspiration: Impressive environment in Minecraft
Tutorial: The best stylized water I’ve seen
I’ve used Nino’s procedural tools for years. A few days ago, I caught his talk at Blender-con, at it was one of my absolute favorites.
He goes into the details on the prettiest stylized water I’ve seen. Both technically and artistically, this is a masterclass.
You can buy his tools for cheap here. They are every good.
Tip: Viewport shading settings
This tip comes from my friend Jan from Alt Tab.
Go to Eeevee, and downscale the render settings. This is what’s used in the material preview mode in the viewport, and you want it to be snappy.
Then change back to Cycles and save default scene.
I’ll add that you should probably add a glare node in your default compositor, and turn on the viewport compositor. It makes it much easier to judge brightness values.
In the performance settings, remember to make the compositor use the GPU.
For the Hi-rez assets, What would be the thing that would have the greatest impact on final quality picture, to prioritize it to be hi-rez above all the other assets if you have to cut corners? I bet that would be final picture size/compression, but beside this? HDRI size? textures rez? (I think textures rez has almost no effect if you don't get close to the thing, right?), caustics (please no...), bevel/small actual geometry details like displacement, number of light bounces?... Obviously that will be heavily scene dependent, but maybe there is a general guideline?