Plant, I’m rally happy to hear about your success. It’s going to be a great 2022 for you, I can tell.
Any CF workout in any 80/20 plan is designed to increase or maintain FTP. The higher you can maintain the intervals in upper Zone 3, the more likely you are to increase FTP. Performing the intervals at mid-zone 3 is more of an FTP maintenance workout. But, it only works if you can maintain all intervals at the same level of zone penetration. Performing the Z3 intervals at 99%, 80%, 90%, and 85% penetration of Zone 3 will not give you FTP improvements the way 95% for all intervals will.
Yes, strength training during an IM plan is just as important as during an Oly plan. It’s better to pick a Level 2 plan with strength training than a Level 3 without.
But, our plans will not improve FTP the way a dedicated cycling FTP will. If your goal is to improve FTP, I’d go with a competitor’s FTP plan for now (we’re about 3 months out from 80/20 Cycling plans, including FTP…).
But remember, a dedicated FTP plan will of course mean you’ll be losing ground in your bike and run. That’s normal and expected. You can gain more FTP with a dedicated FTP plan, but you can still gain some FTP with a competent tri plan.