How do you have your processors and memory allocated?
6GB reserved for other apps.
Reduce cache size is off.
Multiple Frame Processing is off, since it seems like it takes so long to "initialize".
I have a total 16 virtual cores too if that helps.
Render and RAM preview times aren't really an issue for me, I'll get laggy GUI responses even if I'm doing something that doesn't involve AE rendering or previewing a frame. It's not totally consistent either other than I never have this issue in 8 bit mode. Also as far as I can tell, having other apps open or closed doesn't seem to make much of a difference, other than running premiere pro and AE side by side after awhile tends to bog things down, but that's expected.
What sources do you use? If you use multichannel EXRs with EXtractoR, that alone would account for a considerable performance loss. The more files/ layers/ buffers you use, the more noticable it gets. AE sucks at dealing with EXRs even in CC, though it's marginallly better there...
No EXR's I use16bit PSD sequences for 3D renders and Proress 444 for video files. I do tend to use a lot of layers, and precomps. I've heard speculation in the past that sometimes just having a lot of keyframes in a project (even if they are in another comp or layers that are turned off) will tend to slow down even simple tasks.
Keyframes don't necessarily slow down things. Drawing them in the timeline when revealed does as does having a layer selected and drawing the path in the comp. Moderate amounts of keyframes you create manualyl should never be an issue, potentially only tracking data or data imported from a 3D program that creates a key for every frame would consume so many resources that things get slow. Other than that your issues may simply relate to color space conversions. If you use fast previews and your graphis hardware is limited, converting the actual 16bit images to float and then again for the hardware accelerated drawing may entail lots of extra steps. Setting your comp to Final Quality and using software rendering mode may take care of that. Naturally there could also be similar issues with the ProRes files in addition to the usual performance issues with any clip-based format... I'd definitely look in that direction more than anything else...
Yes, the bulk of the keyframes are generally from imported objects from C4D which put at least 1 keyframe per frame per layer. I didn't realize there were so many extra computational steps with this color workspace, I guess I thought the Linear workflow was a more "pure" workflow, but admittedly I only know enough about color spaces to keep things consistent.
I'll try the Final Quality option. Also I just saw under Prefs > Previews > Viewer Quality, there is a "Color Management Quality" option there. Not sure if fideling with one of those options will help too.
Other things I've thought of have been my OS drive vs. Render Drive vs. Assets drive. Currently I have a traditional spinning drive for my OS, and I'm connected to a SAN via fiber which is roughtly 350MB/s on the best of days. I have my scratch set to one volume on the SAN and my assets are on a different volume on the same SAN. I did that because writting to a seperate internal drive for scratch/cache is going max out at 70MB/s.
I've been thinking about investing in a solid state drive that sits on a 16x PCI slot and using that for either my OS or my scratch/cache drive.