Thanks. The post processing shader is doing must of the heavy lifting.
As for the build size, there are multiple factors contributing there. I used to do the seasonal gamejams hosted by Epic Jams, where builds under 100mb were their own subcategory. I learnt lots of optimization tricks from there. These tricks include ticking options in the project packaging page such as ‘Create compressed cooked packages”, “Cook only maps”, “Share Material Shader Code” and “Shared Material Native Libraries”. Then setting up a list of maps (or scenes if you prefer that terminology) to include in the build, under the “List of maps to include in a packaged build”. And similarly setting up a list of “Directories to never cook” under the homonymous category, to make sure unwanted large assets find their way in the build. I also use “Directories to never cook” to blacklist engine directories that I know aren’t used in my project. Directories such as “/Engine/Tutorial”, “/Engine/VREditor”, “/Engine/EditorLandscapeResources” and “/Engine/EngineSky”. In theory none of those directories should affect build size regardless, but I did notice my build size got lower regardless when I explicitly blacklisted them. Likewise, I go through the Plugins options menu and disable anything I don’t use. VR plugins, that used to be enabled by default in UE4, are probably the worst offenders. Not only they take up a bunch of space in your build, they are really annoying if you launch a non VR game on a PC with SteamVR installed. I believe the cable component and CharacterAI plugins are also relatively large. Nowhere near as bad as the VR plugins, but I’d disable them if they’re not being used. Finally, I do use Unreal 4.26. This version allows me export Windows games as 32 bit executables rather than 64 bit ones. The 32 bit export shaves some megabytes off the build. The downside with 32 bit builds is that the game can only use up to 4gbs of RAM that way. But realistically speaking, 99.9% of gamejam games will never need even half of that. And a 32 bit executable makes what I make playable on very old machines too. And if I ever need to make a 64 bit build, I can just do that in UE4.26 too. These are also the reasons I’m not touching UE5. As a solo dev only interested in stylized games, all the crap introduced with 5 is completely useless to me. On top of that, benchmarks posted by other UE devs on social media clearly demonstrate that, even with Lumen and Nanite disabled, taking an UE4 template project and upgrading it to UE5, only results in reduced framerates. I don’t have the resources to compete with games chasing cutting edge graphics, so I gotta play to my strengths. And I prefer an engine like UE4.26, that allows me to make games that run at better framerates and work on older machines too.