I use the Lowepro GearUp PRO (I think in site L) inside my various hiking/mountaineering/climbing backpacks.
Pros:
The pouch can move between backpacks.
My backpacks are lightweight and optimized for their specific use case. Examples are comfortable belts, gear loops, holders for hiking poles, ice axes, cramp-ons etc.
Enough space to fit my mirrorless setup with a few lenses and powerbank and/or drone, but not too much space so I do not bring more than the essentials.
I have backpacks with easy side-access so I can get to the big side zipper if the Lowepro very easy.
Cons:
Depending on the backpack it can be a bit more work to get to everything.
Not too much space to fit stuff, so my action cam and drone remote usually have to live somewhere else in my backpack.
I use the Lowepro GearUp PRO (I think in site L) inside my various hiking/mountaineering/climbing backpacks.
Pros:
Cons: