Update: lighting/shading is seemingly way more taxing on the game's performance than in prior builds, even with IES, console table lighting and sun rays all disabled. The issue seems to stem from the "Rendering features" option in the graphics settings, which determines the quality of light sources such as drives, tower and satellite beacons, and keypads. I tested my theory by filling a drive rack with level 3 drives and placing it on the signal searching desk, and the game dropped from 80 frames to 40 when I stepped back to fit the room in my FOV.
My assumption is that, like other options and save settings, the game isn't retaining the setting for it and applies the highest quality lighting even if set to "1". Disabling the rendering makes it impossible to determine if doors are locked or towers are online. If I could make a suggestion, it would be adding static color indicators with no light source for keypads and drives, so that they aren't stacking and chewing through PCs that are mid-to-low tier builds.