So the initial steps prior to the Kreb's cycle occurs when glucose is metabolized to pyruvate, and then pyruvate is metabolized to acetyl CoA, and that is then used in the Kreb's cycle.

IIRC you get a total of 38 ATP per glucose molecule metabolized via the Kreb's cycle...but it's been a while... 😃

There are some alternative pathways (e.g. via ketones) but those typically only are leveraged in extreme circumstances (such as starvation).

However, the typical pathway for cellular respiration leverages glucose.