I'm torn about refills to be honest.

One of my first tasks at my first job, like 25 years ago now, was to scrape crud off of a LaserJet 4 fuser. My boss explained that they tried using remanufactured toner cartridges to save money, but they found that these would deposit crud on the fusers. Thanks to tight budgets, we ended up scraping the crud off of the fusers using a screwdriver and only replacing the fusers if they were too far gone. They had switched back to HP cartridges before I started there, but the results of the remanufactured cartridges were still around for a few years.

We also used a product called Rubber Renue to rejuvenate the pickup rollers/pads as a bottle of that stuff (which lasted a LONG time!) was significantly less expensive than the maintenance kit that contained the new rollers.

The savings for that refill kit are significant, but I also don't want to potentially ruin my unicorn printer.

You can also send them away to be refilled! Have done this for high use lasers for years. https://inkjet411.com/?page_id=4779

I always worry about inhaling that stuff if I refill.

Am I being paranoid? Genuinely curious.

Same.

Where I landed is that it's simply not worth the risk given the relatively small amounts involved. IIRC I bought an off-brand toner once -- the smell when printing was definitely stronger. Replaced with a genuine toner quickly.

I've done this... It works, but is messy.

Yep. As I said to the OP, you can also send them away to be refilled. For office environments, you have two sets of carts that can be swapped and filled.