Mike,
First off, welcome home.
Two weeks isn’t enough time to build up much (if any) new fitness. Though you may notice when you start doing some of your ‘old’ workouts that you’re actually feeling less fit than you were before you left for Denali. This comes as a surprise to many people, but is actually common. The training is designed to increase your fitness, climbing Denali is more akin to exercise in that it’s not modulated or timed in a way that increases your fitness. So, to answer your question, the best thing to do in the time that you have is probably aerobic capacity work. Meaning 3-4 workouts at a heart rate close to, but below, your aerobic threshold. AKA Zone 2. (search ‘aerobic threshold’ on this site if you want more info about that. Ideally hiking up/down hills with weight in your pack that is 50-70% of the pack weight you will have on Baker and Rainier. After that trip, you’ll probably want to re-start your 16-week plan again after a week or two or R and R.
As for the acclimatization: The rule of thumb is that you lose it at the same rate you gain it. So two weeks of adaptation to 14k will be gone in about 2 weeks. This varies between individuals, but generally holds pretty true. Don’t expect to run to the top of Liberty Cap on your first day in the NW. Climb Baker first, then go to Rainier, camp mid-way, and you’ll most likely be fine in terms of altitude.
Enjoy!