ATLAS is not a game for low-end PCs, that much is clear, but that doesn't mean you can't optimise the experience a tad bit better if your rig isn't quite up-to-par.
ATLAS low memory mode is a special toggle that you can opt into using which will - in theory - make the game more playable on a rig that uses less than 16 GB of RAM. Down below you'll find a handy guide on how to use it.
Since ATLAS is running in Unreal Engine 4, there's a wide variety of line commands players can employ in order to try and have the game perform better. One such command is the aforementioned low memory mode, and it may well make or break your experience playing ATLAS.
If you're wondering how to turn on low memory mode in ATLAS, fret not, as the procedure is fairly simple: all you need to do is go into your ATLAS launch options on Steam and add '-lowmemory' to the line. This will launch the game with reduced effects and such, optimising it to run better on less-than-stellar gaming rigs.
You can also add some other options to the mix, too. '-sm4' will force an older Shader Model to render the game's graphics, while '-d3d10' will kickstart ATLAS in DirectX10. Using these in conjunction with low memory mode may well improve your playing experience, so give them a shot.