Jim, the answer for you is the same as the answer for anyone: boot fitter. (Note to The Internet: I have skied with Jim a bunch of times.)The OP is quite a good bump skier, also skis trees frequently and fluidly.
I am in the market for new boots too. In 50+ years of skiing I've never had a stiff boot, and I've been on a pair of Lange 90 flex for last nine years. I am also interested in more discussion on the tradeoffs in performance between stiff vs. soft boots. I don't race either. I do like to ski bumps, trees, and pow, but at about half the speed and skill of @SCWVA . I do occasionally feel like I'm bottoming-out (mushy) in my 90 flex boots in moments of high exertion, but some of that might be due to their age and wear. I use the same stock liners that came with the boots.
Scott's comments are great. I agree with them, fwiw. Doesn't change the core answer.
My most recent pair, from about four (?) years ago, happen to be Lange RX130s. I am 5'7" 140. You know my quirks. I honestly don't think my boot fitter thought too hard about the flex. He probably just figured he could soften them if needed.
Without a great fit and suitable forward lean, these boots would be WAY too stiff for me. As it is, they're awesome (except for the cracks - different thread). Another way to say what Scott and I are both saying is, "if the boot feels way too stiff, it's probably more about your setup than the actual shell stiffness." I know that for me, if I don't have enough forward lean in the boot , or if it's even a little too big, I can't flex it even if it's a 90.
Edit: probably worth adding that if a soft boot worked best for me I'd be on it in a heartbeat. There is no machismo here. I'm on pink skis FFS! LOL.