Working as efficiently as possible in the Adobe programs?

Depends on excatly what you are doinmg. You can save as a .ai file and turn off pdf compatibility. Thsi will make the file much faster and smaller. You can save as and utnr back on PDF compatibility once you are ready to import into InDsign or Aftere Effects.

I would  recommend using the .PSD format for importing images into AI. You have nonlossy compression, adn edits are quick easy to make using .PSD placed workflow. Also link to images don't embed. Dont use old type 1 fonts they are problematic.

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@Corrupt abyss wrote:

2. Where can I find the patch notes/what's new from previous Illustrator, InDesign, and Photoshop updates? I know how to see the most current "What's New" updates but is there any way to see additions from previous versions of the applications without going on YouTube?

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When you are on the What’s New page for any Creative Cloud application, scroll down past the latest changes until you get to the Previous Releases heading. The one for Illustrator covers eight releases going back to 2019. To find changes from releases earlier than that, sometimes I check the version history on sites like Wikipedia.

As for #2: https://helpx.adobe.com/illustrator/using/whats-new.html

As for #1: You have to analyze the task you have. And then you analyze how you expect your workflow to be (like: do you expect artwork to be editable or do you expect input from a database or the like). And then you analyze what kind of result you want to have. And then you have to analyze the methods Illustrator has to offer. And then you decide.

There is not "the" single most efficient function.

Except maybe Live Paint 😄