An initial view of the ProTactic BP 450 AW ii Tactical Camera Backpack fit with a Nikon Z9. It demonstrates key/core features as well as some details you won't find in other review videos for this product. It also teaches life lessons.
For example, embrace the suck when it comes to trying to customize the padding/walls inside. Although you can move or remove divider walls, they sort of mostly appear to be intended for the original spot in which they were placed. But don't be chicken when it comes to bending stuff in a weird place to make it work for you. And try to minimize how many times you move these walls around. Your backpack interior will thank you.
One technique might be to
1. Remove all of the divider walls from the bag.
2. Put strips of painters tape over all of the velcro parts of the divider walls.
(maybe leave just a small portion of each velcro strip exposed).
3. Place each divider into place - thinking about where the weight will be placed while the backpack is upright (what's going to sag or get squished).
4. Place your gear in preliminarily to check the fit, etc.
5. Un-tape the velcro strips one at a time as you secure each piece into place.
6. Check that everything fits again.
Hope this helps.