Styles in addition to blues harp.

OK, quite the bundle of questions!

It pays to gain fluency in the use of both tongue blocking and non-tongue embouchures, as each can do things the other can't.

There's a particular ornament in fiddle tunes that amounts to nothing more than a fast repetition of a note, as in three iterations within a fast-moving beat, usually two sixteenth notes and an eighth.

When I first started playing fiddle tunes, I tried to do this with a tongue block, but it came out slow and ill-defined - clumsy, in a word. So for that one ornament I would switch to a pucker and use a diddle-di tongue action to play the ornament quickly and crisply. Then I'd switch back to tongue block, especially if I needed to make quick back-and-forth leaps with corner switching.

Classical players like Robert Bonfiglio defaults to tongue blocking and uses a lot of corner switching, but also uses pucker for some special effects. Another use is to give you a third embouchure point, in the middle between the left and right corner points. So you could do a leap of, say, C (left corner) up to Bb (middle, aka pucker) up to E (right corner) cleanly and rapidly.

Bending is used in many styles of music, and on chromatic. However, you need to consider how (and whether) it can be used in a way that fits with the style of music. Some Irish fiddle styles use a sort of slurring bend, but many styles do not. And as a harmonica player you may be looked at askance if you appear to be bluesing up an Irish session inappropriately, so you have to be careful not set off the built-in prejudices that some trad players harbor toward harmonica players. Once they know you're solid on the tunes, they may relax, though.

In blues chromatic specifically, you do hear bending, just not the way or to the extent you hear it on diatonic. You may hear a little sliding into a note from below, for expressive purposes, but the sound of a bend on chromatic isn't as exciting on its own as it is on diatonic, and you don't need it to supply missing notes, so it doesnt play as prominent a role.

For some examples of chromatic bending, check out a few examples:

The way Stevie Wonder bends notes on Chaka Khan's "I Feel For You", starting around 1:41 - especially the first note of his solo around 3:45 (the extended dance single has a longer harps solo that the radio version).https://www.youtube.com/watch?v=tTwKsJv90Gw

Check the way Jerry Murad of the Harmonicats bends C all the way down to Ain the first phrase of "Cherry Pink and Apple Blossom White." This bend is in the oeiginal trumpet lead of the Perez Prado version, but Kim Wilson couldn't do it in Blow 6 on a diatonic and just kind of held the note for a long time.https://www.youtube.com/watch?v=z7vG3hyqrvg

Little Walter didn't often bend on the chromatic, but here he does, on Teenage Beat. Again, it's subtle:https://www.youtube.com/watch?v=iXVQzwVvSLA

I'd also suggest checking out the Suzuki SCX-48 and the East Top models.

The 12-hole size of chromatic is a bit easier to get started on, as it's not so dauntingly huge as a 16-hole model, while offering the same three-octave range as a standard diatonic. You can get 8-hole and 10-hole chromatics, but they suffer from a range that's a bit too restricted once you really get going on the chromatic.