When is the "correct" time to use the less formal Sarge? Chief?

It's probably best to just stick to sergeant.
It's also not a good idea to refer to your supply sgt as "Sugar Daddy".

When you want to do extra PRT because you didn't do enough in the morning.

When you make E4 and have known them at least 2 yrs. LOL

SGT (Join to see) Never, unless a Sergeant tells you that it is ok, and then only to him or her. In the Marine Corps, this would be unacceptable.

Never as a private, only if equal rank and friends or buddies.

Don't ever call me Sarge, unless we are the same rank or you outrank me....

Don’t.
Really truly just don’t.

The Sarge thing is extremely unprofessional, I earned my rank and the only reason I don’t blow my top off when I’m not addressed by my actual rank is because it’s the army norm for all E5-E7 to be called Sargeant.

I busted my ass for rank and I’ll be damned if anyone makes a joke out of it

Chief is reserved for CW2-CW5, in the Army. Dont call a Navy WO "Chief", as their senior Petty Officers (NCOs) are "Chiefs". WO1 is Mr/Ms "insert last name" or Sir/Ma'am.
As for Sarge...no...just no.

The biggest problem I read here is about respect. Gentlemen, we all have had to earn the rank that we wear. Most of my warriors call me Sergeant the rest call me Messdaddy. To answer the question to this young PFC, show the rank the respect it deserves most of the time it will be returned. I was always told that "Sarge" was a bottom feeding fish. Mostly I call a SPC Sarn't to prepare them for the next step but I address a NCO as Sergeant. 1SG as such unless told otherwise requested. Warrant Officers 1 dot- Mister 2 dot and beyond is considered Chief. Hope this kind of clears things up for you PFC Robert Cubilla

Uhm maybe never.

I was secretly hoping Sarge would finally die with Beetle Bailey. Even as an Officer I referred to NCOs as Sergeant, First Sergeant (never top), and Sergeant Major as appropriate.

Referring to Warrant Officers as Chief varies by Officer. The Warrant Officers that helped raise me were always Chief. Start with Sir/Ma'am until you figure out who you are dealing with.