You may want to read this by SteveH: https://uphillathlete.com/forums/topic/denali-climbing-questions-pace-and-gear/
He says the following about Diamox: “A word about Diamox. Diamox is a diuretic prescription medicine that very popular among high-altitude climbers, including Denali climbers. Frankly, I think there is a huge placebo affect at work with Diamox. I’ve been to the top of Denali something more than 20 times, and when I was in my 20’s, my fellow guides and I experimented on different trips with and without Diamox. For me (and keep in mind that different people are likely to react differently to the affects of a drug.) I had to come to the conclusion that Diamox did nothing for me in terms of speeding up or aiding the acclimatization process.”
I also seem to recall that Steve and Scott also did not not think the side effects of the drug were worth it, even if it does something for altitude?
I’ve been up Kili over 6 days, if I recall. What makes a huge difference there, depending on your guiding setup, is porters. I was strolling with a pleasant daypack, while seeing locals all around me slogging uphill with a big pack on their back, another pack on their front, and a cast-iron cooking setup on their head. No fancy gear, they weren’t even wearing sneakers even in some cases. Humbling stuff, makes you reconsider your place in this world…
I agree with you that 14k and 19k are different. In addition to the style question over using diamox, I would try it at least once before your actual trek to see how you feel and react to it?