i can't agree with what you've heard. there are two issues to address here:
the first is the instep feel. do you have an insole in there? if you don't i highly recommend starting there for this problem. i am not really comfortable in any boot until my arch is supported and my instep is properly aligned.
the second is the tightness in your forefoot. this could be related to your foot position in the boot - putting in an insole will help to hold your foot farther back in the heel pocket (as well as angling your foot up and back slightly), which makes it sure seem like there's a little more room up front. this will pull you out of the front of the boot a little more. it will help.
the liner can also help you with this problem.
as for the liner expanding to fill voids, yes it does this when heated. however, after you put your foot in there, tighten it down, and wear it for about 12 minutes, the foam will "compact" where your foot requires it to and remains as a "void filler" where there is extra space. after the "hot form" process is over, ie the liner feels cool, take the boot off, let your feet recover, and put the boot back on. you will be amazed at the difference - it pulls you back into the heel pocket and makes the boot "feel" longer.
this years' hot form has a larger "hot form" area in the liner, but it's really still mostly in the heel and through the mid-section of your foot, not as much in the toe box. however, the longer "feel" will pull your foot back in the boot, helping to reduce the unwanted pressure.
do the hot forming after the insole has been installed. if you want to see how the boot feels without hot forming again, you can simply plug the boot in at the shop and let it cool down without your foot in it. compare that fit with the "hotformed" fit and then re-form it to your foot. one of the cool things about this liner is that it can be formed and unformed with no negative effect on the liner's material.
hope this helps.
before panicking too much more, finish the fit process of the boot, and see how it fits then.