That is a great post from Jive1.
I think in terms of chord progressions and like to understand what's happening "theoretically". Helps remember the tune, give you a framework for your library of grooves and fills, and compensates for my average ear. Whatever you need to do to get there is ok in my book.
A few other common chord progressions to add to Jive1's list:
1. R&B style where major chords are stacked on the minor pentatonic intervals: I, bIII, IV - for example C major, E flat major, F major. Could go back to I, or continue via bVII, or to V, bVII, or sometimes via bVI like Gimme Some Lovin. Or go around I, bIII, bVII. I think a few Beyonce tunes do that.
2. Related but more riffy: I, bIII, bVII, IV. Super common.
3. Three types of IV-V cadence progressions built around tonic, minor chord, then IV, V. These use the three available minor diatonic chords as the second chord in the sequence:
(A) the do-wap sequence Jive1 mentioned of I, vi, IV, V. Very common.
(B) More soulful version of I, ii, IV, V. Gives a plagal flavour as II and IV are closely related.
(C) Chord III tunes, common in folk. I, iii, IV, V. I love tunes with chord iii. Watch out for substitution on the major III too. Quite common, even going to IV, V, rather than as secondary dominant to vi.
4. Nested fourths. Hard to explain but super easy to play. For example: I, IV, bVII, bIII. So basically a starting note, then a fourth up. Go down two frets and repeat. If something sounds cool with lots of apparent leading voice movement in the bass, it could be this. Make the first chord minor and it sounds even better. Sometimes found in bridge sections. Try the minor kick off and see if you think of the same tune as me
5. Tennessee Whiskey. I, ii, IV. Yup, should be able get that one. Break out the ii minor pentatonic and IV major pentatonic for the fills. They're the same thing. Sound pro in one easy step.
That's a segue into the bit I've been working on lately of how to improvise lines and fills across those patterns. On the R&B sequences, pedal phrases or fills using the minor pentatonic of chord I will overlap a lot of the other chords as major pentatonics. Can extend chord I as a minor 9th for example, adding the D to the c minor pentatonic to fit with chord VII. On chord bVI I tend to use major pentatonics, which closely fit. Also can be used in same pattern on bVII which often follows. If bVI is moving to V then I tend to do minor pentatonics on both, but favouring the fifth and octave.
As a rule of thumb for R&B it's usually minor pentatonic (and blues scale) on chords I and V, and major pentatonics on the rest. Ends up being similar notes.
On plagal flavoured tunes there's heaps of scope overlapping major pentatonics. And with tunes like Angie and Wild Horses you can do that while also using minor pentatonics on the "sharp" chords like the secondary dominant to the relative minor.
I tend to avoid minor pentatonic on chord IV (or at least the flat third degree, unless it's minor iv of course), and use either major or minor on chord V depending on flavour needed.
Walk ups and walk downs are a choice between diatonic or chromatic. Flavour to suit. Understanding the tonality and key centre helps with the diatonics. Just scales really.
Probably made this sound more complex than it is, but opening up my hands with major pentatonics especially has been a game changer for me. It's helped unshackle me from rote learned phrases, and not getting stuck in the box.
Try out the chords on keyboard, it's easier to see and hear in the first instance. Trying to imagine the whole chord while just playing one note is not always easy until you build up your chord bank memory.
Another pointer from Dan Hawkins: Try thinking of fills as rhythms, and the notes will find themselves.