> He's also very much into pushing the engine's lighting to its limits.
With a bit of experience you can achieve global illumination results that are competitive with Pixar films by using static scene elements, URP, area lighting, baked GI and 5~10 minutes on a 5700XT. The resulting output will run at hundreds of FPS on most platform targets. If this means pegging vsync, it may also be representative of a power savings on those platforms.
Lights in video games certainly use real electricity, but the power spent on baked lights is amortized across every unique target that runs the game. The biggest advantage of baking is that you can use an unlimited # of lights. Emulation of a physical scene is possible. There are also types of lights that aren't even accessible at real-time (area/volumetric). These produce the most compelling visual results, avoiding problems that others create such as hotspots in reflection probes and hard shadowing.
Lightmap baking is quickly becoming a lost art because realtime lighting is so simple by comparison (at first!). It also handles a lot of edges cases automagically. The most important ones being things like dynamic scene elements and foliage. Approximately half of the editor overlays in Unity are dedicated to visualizing the various aspects of baked lighting. It is one of the more difficult things to polish but if you have the discipline to do so it will make your game highly competitive in the AAA arena.
The crazy thing to me about baked GI is that it used to be incredibly crippling on iteration time. Working at a studio back in 2014 I recall wild schemes to bake lights in AWS so we could iterate faster. Each scene would take hours to fully bake. Today, you can iterate global GI in a fixed viewport multiple times per second with a progressive GPU light mapper. Each scene can be fully baked in This tech doesn't have to be all-or-nothing either. Most well engineered AAA games utilize a mixture of baked & real time. The key is to make as many lights baked as possible, to the extent that you are kind of a constraining asshole about it, even though you can support 8+ dynamic lights per scene object. I look at real time lighting as a bandaid, not a solution.
If you want to attack this from a business perspective - Bleeding edge lighting tech is a nightmare if you want to ship to a large # of customers on a wide range of platforms.