Problem:
Elytra clips with and covers backpacks.
I have been trying to combine mods that will allow me to use the elytra and travelers backpacks without it looking bad to no avail.

Solution 1:
If elytra is in backpack allow it to auto equip when trying to fly and unequip when landing making it look a little like buzz lightyear's deployable wings.
Similar to this mod (AUTO ELYTRA https://www.curseforge.com/minecraft/mc-mods/auto-elytracould) but with out swapping armor and elytra or swapping elytra and backpack. Maybe with a second curios back slot that it auto equips/unequips to with the help of this mod (ELYTRA SLOT https://www.curseforge.com/minecraft/mc-mods/elytra-slot).
Could be an upgrade or an option in the config.

Solution 2:
New backpack and model that incorporates the elytra wings and mechanics as its special ability for seamless backpack and elytra usage.

Combining two items utility and appearance is not possible, that might result in many compatibility issues, I'd suggest to just switch the backpack visibility while equipped the elytra. You can do that from equipped backpack's settings menu