Need help on saving memory for very large video

I'm working on a large scaIe video. I just have a few questions as I am experiencing memory problems and crashes. Just shooting some ideas with people who understand the bottlenecks of the AE. 

I have a about 300 objects in the design which is part of the logo.  I got this really nice wipe effect that which uses a gradient controller to driver the opacity. So it looks really great when effected.

This involves putting  in this onto  opacity:

C = thisComp.layer("grad").sampleImage(position,[.5,.5],true,time);
L = rgbToHsl(C)[2]*100

Are expressions more computational that regular key frames? 

With vector images,  does after effects have to use a lot of brain power to 'contiuously rasterize' a small illustrator file by 1000% closer to the size need. Is it better to upscale in illustrator before?

There other things like switching  colour profiling to 'fast' which I'm looking at. 

And 'hardware Accelerate' options. I'm not sure if it is making much difference yet.

Thank you in advance

Julian