Adobe CC version compatibility and older Macs

Hi all. We're in a compatibility-crucial graphics department, and will soon have users on MacBooks with High Sierra and the latest/greatest Adobe and Suitcase products (although not just-released Suitcase 9 yet), and users still on mid-2010 iMacs currently running El Capitan, Adobe CC 2017 apps, and Suitcase 7.

Background: Our department recently purchased the MacBooks. I've been planning the installation of the latest full Adobe CC (emphasis on Illustrator, Photoshop and InDesign) and Suitcase 8 with Adobe plugins. We were about to purchase iMacs for users currently on mid-2010 iMacs when the top CEO dropped a BOMB: No more purchases for any business unit until some time in 2019. Grr.

So I'm trying to figure out how to ensure compatibility in a "holding pattern" until we can get the new iMacs, with a minimum amount of fuss both now and later. My questions are:

1. Will users on the old mid-2010 iMacs running Adobe CC 2017 products be able to open documents created/modified on the new Macbooks using Adobe CC2018? Can I just leave those old Macs alone?
   1. If so, does Adobe 2018 install fonts that would have to be added to the old iMacs for maximum compatibility?
2. Or am I better off putting Adobe 2017 on the new MacBooks, assuming I can find a link?

I did find a tech doc stating that Illustrator 2018 requires at least Sierra: Adobe Illustrator system requirements ) And Suitcase 7 doesn't work with Adobe CC 2018.  So putting Adobe CC 2018 on the old iMacs opens a can of worms.

(How much easier this would be if we could just get those new iMacs, but try explaining that to an executive near the top of the food chain who nonetheless espouses continuous improvement and "work smarter, not harder".)

Thanks.