Well from the department of things that make you go hummmmm.
First is this for an environment for a game or is it for visual reproduction?
The difference is for a game the level of detail “could” become a problem as to performance but considering all things that could effect performance my workflow habit is to go high and then cut back if performance does prove to be a problem using a superior testing tool called my eyes.
My rule of thumb is to go high as it is easier to make it less than it is to try and make not enough do more once you have enough of the environment built up where you can start deciding what to spend resources on and what you can not afford. This is why there is this thing called iteration.
As far as the example goes it’s performance is not going to be an issue as for the most part it’s just a fly though of a bunch of walls so for sure more could be added as mesh detail.
As for the build it’s self it is rather simple and I assume uses a single lighting solution and sky light to fill the halls and maybe a few kicker lights so if you can figure out the buttons as to lighting first then that would be about 80% of the work needed.
Next what has a realistic flavor really depends on the rendered output. What looks real is easy enough as a static render but once things start to move is where you can sell the realism using pro production values as the guide.
Although the example is good where it fails as part of the selling of the visuals is having the camera “FLY” through the environment at game speed waving that camera around like some magic wand at 30 FPS does no favors as to quality of image.
Granted YouTube chews up quality even at so called HD levels but for crying out loud slow things down as by doing so one is rushing past the details yet to be fully formed as being reactive to lighting.
That being said what looks real and what does not depends on how light reacts to surface and materials once objects or camera begins to move and a lighting detail, spec gloss bump, could occur as fast as 1/100th of a second or only last 4 or 5 frtames in and out of it’s formation so if blasting along at warp speed at 30 fps then what makes for an excellent static shot is lost in the blur of moving images.
Soooo as a must do tip as to a fly though go slow, render out at 4K resolutions, and at least render the master out at 60 FPS (I general go 120) as at that quality level and speed what should make things look real have time to properly form if you don’t ride the camera like it was a jet rocket. Follow this one tip and one tip only “will” add at least 50% to the over all quality…once you start moving stuff around.