The half size up is snug, but my toes are still able to move around. When wearing boots, are toes supposed to have wiggle room? How big is the "pack out" is it a small change like half a size? (I have the Impact 3 liner from Burton).
Pack out is usually about a half size, so if you think your foot will still be snug and not move around after the liner packs out then you're probably good. When I used to fit people I would usually try to get their toes so that they were just barely skimming the front, not firm against the front or scrunched up, but just barely, barely touching because the liner will pack out. Every brand and model's toe box is different, so you will be able to wiggle your toes more or less depending on the brand and model and your foot shape (wide or slim), and you should be able to move them a little bit otherwise you will have circulation issues and be uncomfotable. If you kick the foot forward while the boot is on the ground and you feel your foot slide forward inside the boot, or if your heel lifts at all when you step then either the boot is too big or you need to tie them tighter. If your foot stays put and all the other criteria is met then you have a good fit. But remember to take my advice with a grain of salt because I am not there personally fitting your boots and you are the only one who really knows what's going on down in your boots and if it feels right. And I promise I'm not trying to make you second guess yourself. I'm just a huge fan of happy feet because your day really can depend on how your feet feel. Sorry for the long winded answer, but there is a lot more to boot fitting than most people think or take the time to consider