I have the original LowePro Photo Trekker backpack, which was made in Ireland, it is about 18 years old.
I at one time ran an RB with three lenses, two backs, four filters (glass), and twenty rolls of film.
It is probably the best way to carry stuff, but there is a downside if you're traversing muddy paddocks. You have to put the backpack on the ground to open and remove stuff, carry a ground sheet that is handy.
I also at another time, used Nikon F3 bodies (2) and a range of lenses from 18mm through to 600mm. Basically the weight of that lot stretched the capabilities of the backpack and the stitching started to rip and seams were opening. I still have it and it needs repair, but it was and is great.
Ensure you have a good waist belt section whatever type of back pack carrier, otherwise your back may end up in trouble.
Mick.