Illustrator CC (both 2017 and 2018) performance vs CS6 (Mac)

I'm trying to figure out how to improve the performance of Illustrator CC (both the 2017 and 2018 versions, latest patches on each). I have a demo file with several elements on it, and about 20 links out to PSD files. The AI file is 7MB, and the total packaged file (including links) is about 65MB. Nothing too crazy.

What I'm seeing: when I switch from another application to AI, the screen takes a moment to redraw. We're talking ~1-2 sec, but enough to be annoying. Additionally, when I drag elements across the layout: Sometimes it's perfectly quick, while occasionally I get a 1-3 second "pause" as I wait for AI to "catch up". I see the same when moving elements via the keyboard arrows.

On the same computer, AI CS6 does not exhibit these behaviors. Screen redraw when switching from other apps to AI is instantaneous, and element moves are similarly instantaneous.

I've observed this behavior on both:

- (An admittedly underpowered) 12" MacBook (2015) with 8GB of RAM running macOS 10.13, and

- A 2017 27" 5K iMac (non-Pro) with 32GB of RAM, SSD, and 8GB Radeon Pro 580 running macOS 10.12.

Here's what I've tried so far:

- Eliminated network connectivity as a contributing factor by collecting files locally, disconnecting from the network volumes, and working locally off SSD.

- Disabled GPU acceleration.

- Removed ALL AI preferences and started fresh.

- Re-imaged the iMac with a fresh OS and applications install.

- Turned off Anti-aliased artwork in the General Preferences.

- Toggled Pixel Preview.

- Disabled Smart Guides.

- Saved the AI file down to various older AI formats.

The ONLY one of these that seemed to have a positive impact was removing all preferences and starting fresh. But that impact was minimal.

Any ideas on what might give me AI CS6-like performance out of AI CC?