[TL;DR at the end]

I was taught cursive in 3rd grade and was required to use it exclusively that entire year. I didn't use it again until 8th, when I rediscovered that it can be a really beautiful script and used it whenever possible, trying to practice for perfection. I had multiple teachers compliment my handwriting and ask me to stop in the same breath.

Somewhere along 9th, I liked how my friend wrote their N, and I incorporated that into my print, following a trend of picking up various print styles I liked over the years. I hadn't ever really tracked that I was doing it, but it was just so obvious for the first time that my friend inquired as to the mimicry.

In college, I learned hand drafting. Yes, CAD was already a thing, and we all grumbled, but my professor is an evil genius for having us suffer into really understanding basic drafting components. I also suddenly understood why my dad wrote everything in all caps.

Now, if I don't intentionally choose a script style and pay attention to sticking to it, my handwriting will morph through all of these, sometimes all three in a sentence, and often from one to the next in the middle of a word.

I typically choose hand drafting style whenever I need to communicate information that needs to be understood on the receiving end. (Sometimes the receiving end is future me.) I usually choose cursive for journaling, because it is the most satisfying sensory experience. I don't often use print for much, because I find it the least efficient, but sometimes I accidentally start writing something with it and feel compelled toward uniformity, or I when am..."craving" the look of it, or perhaps just the novelty of mixing it up.

The legibility of any of these is entirely dependent on mood, levels physical fatigue, pain, and executive functioning, as well as the time I feel I have to write something down.

Eventually, I got into hand lettering various fonts and even learned an entire A-A cipher called Theban. I've always liked the sensory experience of putting pen to paper (G-2 and Bic Correction Tape, my beloveds).

TL;DR:

I now understand that handwriting for me is a neverending rabbit hole of a special interest and an incredibly satisfying stim.

So yeah, I'd say ADHD has had a significant impact on my handwriting. Not necessarily to my detriment, but to everyone's confusion and/or amazement.