Days in the Life of Bronius: Let there be Light! DIY recessed lighting installation project

I am no electrician, but I had a handy father who was not afraid to do his own home repairs and maintenance, and I had tinkered with electronics since ~6th grade. So when it came time to install recessed lighting in our upstairs fitness studio, it was not a far leap from hearing how expensive it would be to hire a professional to rolling up my sleeves and doing it myself. Besides big savings, what the kids and I learned in the process will stick with us a long time. Plus .. it was really fun overcoming all the frustrations and challenges along the way! As usual, I leaned heavily on expertise of knowledgeable staff at our local Lowes and a few friends.

The primary things I knew going into it:

Safety: Electricity moves through wires, A/C is not DC, 120 volts is not lethal (phew!), a breaker box will save me if I do something stupid, and keep the breaker off while working on the isolated circuit.
Know-how: ~~Copper is ground, Black is neutral, White is line~~. Yeah, ok, I had to relearn this one: Copper is ground, White is neutral, Black is line ("hot"), and so is Red when it exists. (Thanks Joe for catching my flub here!)
Also I had experience cutting perfectly good drywall on a perfectly new home when I installed our cat door a few years ago.

And where I got to level-up (my boo-boos):

14/12 gauge electrical wiring is really, really rigid and hard to maneuver: Leave sufficient slack, and strip with generous lead.
Not all 6" LED housings from the same company are the same size. I bought four in two styles with the intention of sampling and swapping once we decided, but we kind of locked ourselves in to the ceiling hole sizes once I had all four up.
But in general my drywall holes could have been just a bit smaller and didn't need the little notches sticking out. Hmm. I could putty and paint these minor flubs some day.

Helper helping in planning :)

Let's go!

The box makes it look easy :)

Severed the 4-conductor ceiling fan assembly wire.. didn't leave myself much play down to the switch into the junction box :(

Original builder did a lot of draping of wires, I wanted to run them through the joists for a more polished finish

The final cut(s)!

The scariest part of the project was placement of LED light fixtures (will they illuminate enough? Will it look silly and uncoordinated in our oddly shaped ceiling?) and the holes in ceiling drywall: