If I go from Terminal D to Terminal A and back to Terminal C, can I stay all post-security (i.e., I can avoid having to go through security again)?

I see I can take transportation btwn the terminals. What's the difference/advantages/cons btwn the Aerotrain and the shuttle (besides what terminal it leaves/arrives at)?

I'll likely be landing at Terminal D but want to go to Terminal A during my 2hr 20m layover. Next flight leaves from Terminal C to Canada. Thinking this was very doable but may reconsider if I have to go through security again because of the extra delay it will cause. I have Nexus/Global Entry if that makes a difference.

Any insights much appreciated!

cheers,