A boot that has less forward lean and stiffer flex is usually a better choice for limited ROM. If we imagine that statement is true...
At your size and weight, with limited range of motion in your ankle joint, you should draw a hard line in your wallet and not leave the shop with any boot, brand or model that is below a 130 flex! There should be a few try-ons of the 140's as well.
If you want to change the effect of your boots on cooked quads, you need to get your fitter to quantify your ankle range of motion and adjust the boots heel height as you are trying them on! Secondly flex has to be 130 or above. And last find the boot that is the lowest forward lean with the highest contact on your shin. ( possibly adding a booster strap to pull the top front of the boot against your shin to give instant and quick power to the ski with the least amount of forward travel )
Keep exploring, your boot fitter is trying boots that they want to sell, not bringing out boot models that address your ROM, Foot shape, or Performance needs.