When it comes to greeting Soldiers E5 and above, does "Sergeant" suffice, or should you always use their full title?

No one had addressed the unofficial titles. Of course we have "Sarge" for E-5 through E-7. E-8 First Sergeants get called, "Top". Finally, at least in units I was in, informally the SM got called, "Smaj" (a highly compressed "Sgt Major", pronounced "Smeg"). No one ever took offense. Now what I can't figure out is that WO-1 through WO-4 are addressed as "Chief". This has GOT to be confusing for the Navy! POs are "Chief". WOs are "Chief". Only the Air Force gets a break on this, as they have no WOs. However, they have a lot of joint bases with the Army and Navy, especially in aviation.

I definitely appreciate all the advice!
Thank you!

Just don't call top "Sergeant." As lower enlisted, it important to communicate through the proper chain of command. If you don't know them I would at least start with "Staff Sergeant". A nice rule of thumb is not to speak unless spoken to, works out good.

In the Army,
e5 to e7, you call them sergeant in response but start by addressing them with rank and title.

E8+ call them by their rank and respond by their rank.

I usually call them SGT and their last name unless it is a 1SGT or SGM

Never say 'sergeant' to a Chief Master Sergeant. Address her as 'chief' at all times.
And 'sarge'? My own feeling was that E's could use the term, but an O would not call anyone 'sarge' because some SGTs might feel that was speaking down to them.

Sgt was always good enough for me. Heck, I don't even think I knew for sure what my correct rank was as an E-6 and E-7.