Mark, thanks for joining in, all ideas are very welcome. For now, let’s not use the term chromatic when going from Ab7 to G7. Let’s call it a bII7 to a I , it will help in as we move through.

Many songs follow the A B A rule; a melody is played, then it moves to something different (melody) and then it goes back to the original melody. Hence A B A
The B part normally travels to the IV of the scale.
Key of Cmajor; C = I F = IV.

C to F --- that move can be made stronger if you use C7 to F. Bb, is the 7th of the C chord. Although you are in the key of Cmajor, C to F puts you in the key of Fmajor, where all the B notes are now Bb notes. When this happens F is I and C7 is V7 (scale of Fmajor)

Now let’s used what we learned: C7 to F can be:
Gm7 – C7 – F or, Gm7 – C7 – F or, Gm7 – Gb7 – F or, C7 – Gb7 – F

When you leave the B part (key of Fmajor) it may be possible to use the same group of chords, but in the key of Cmajor.

It’s gonna get even better, John C.