Would love to have Inventory Tweaks Integration with the backpacks as it is one of my must have mods.

Couldn't you already have that by adding a backpack's container to allowed containers in the .xml file as described here?

I added the following to that InvTweaks File, but it only show the Settings button and will not sort the inventory.
<inventory class="v0id.vsb.container.ContainerBackpack" disable_buttons="false"/> <!-- Other inventories to show just the options button on -->

I'll look into manual compatibility then.

Just a heads-up - inventory tweaks's sort buttons are a bit(5 pixels or so) overlayed on top of the slots. As far as I can tell there isn't much I can do on my side unless InvTweaks impements the necessary hooks in their API. At most I can make it so the buttons don't show up at all but I am not sure about that, I need some feedback on this.

Thank You! Seems to be working fine. The buttons overlapping do not cause any issues for me