I am assembling timelapse footage shot from raw stills, in after effects I choose the 16 bpc then have been exporting the clips as 4k Cineform files in the 12 bit RGBA setting, quality level 3.

is this all overkill, should I just use 8 bit, and a different export codec?
or is the 16bpc going to give me more when I do color correction and effects?
Should I go higher in the AE settings to 32 bits?

My system cant even play 4K 12 bit cinform files, but I just downsample them for editing.

What will your final product be used for? Web? HD commercial? Movie theater showing? Choose your bit depth and resolution depending on the requirements of your final product, otherwise you'll be wasting a lot of time rendering an overkill project that you'll end up downsampling.