Why not use 110V AC for a hotplate and the soldering iron? USB seems silly.
I’ve always had a 110 soldering station, but recently bought a Pinecil portable iron for soldering in the field, and damn that thing is so convenient and fast to heat and accurate, I hardly bother with my full solder station any more
The pinecil is unbelievably good for what it costs. I find myself using it more than any other soldering iron, only pulling out bigger more expensive models when I need more thermal mass. I can’t recommend it enough.
The one downside someone pointed out is that replacement tips are pricey because they seem to include the actual heating element, but even then it’s still such a great device IMO
And, at $25 for a set of four, they aren't even that expensive.
https://pine64.com/product/pinecil-soldering-short-tip-set-f...
Brands like AiXun and Handskit make inexpensive stations that are compatible with JBC C215/C245 cartridges, which gives you a ridiculous level of performance for the price.
Also, don't sleep on knife tips. For a long time I thought that the Chinese phone repair guys were goofy for using them so much, but they were right, I was an idiot and I now use them 99% of the time.
If your product is more complex than a light bulb, dealing with mains power can be quite a hassle. It requires bigger and more expensive parts than negotiating for 20V DC with a USB PD source.
You might want to take a look at USB-C to barrel connector adapters intended to run older laptops on modern chargers. They are tiny and cheap, I use one to liberate a thunderbolt 4 hub from the massive power brick it came with.
USB-C power delivery cables are pretty useful and better than a dozen transformers fighting for space on a power strip.