I'm a bag of the month quitter! There is such a thing as enough/too many, I'm trying my damnedest to get down to 2 or 3. This is where your local camera store really is a gem - take your stuff in and see what fits. See if it matches your ergonomics and holds things where you want. Oh, and buy it from them while you're there.
A GFX plus a few lenses is pretty easy. It's when you're up to 2 bodies, plus 6 lenses, flashes, etc that things get complicated - or you have odd shaped bodies like the XF, H or 645. Things like height, body mass and structure all play in to what fits well.
There are so many different, and often conflicting, requirements for different tasks that it's impossible to fulfil them with just 2-3 bags.
Let's see:
- Airline transport - it needs to protect all your gear, fit within the size limits and weigh as little as possible. Small regional airlines in various parts of the world often have even more stringent carry-on requirements. When you're that close to the weight limit (or over it) and the bag's going to be sitting in the overhead compartment anyway, ergonomics don't matter. F-stop inserts are great for this, since they're removable. May consist of a combination of bags and jackets.
- Wildlife shooting in Africa - needs to be a backpack (since you'll be carrying it a lot), hold large supertele lenses and a full-size monopod/tripod. There probably won't be room for much else in the bag.
- Hiking - needs to hold food, spare clothing, camping gear, etc. in addition to the camera gear. Also needs rain protection. Access to gear may be slow.
- Kayaking - needs to be waterproof (not just water-resistant) when closed. I just put the whole thing inside a roll-top, waterproof bag, but that means zero access to the gear on the fly.
- Travel through risky areas - needs to not look like a camera bag. Tripods and other shooting equipment need to be carried inside the bag. Entrance to the camera compartment should be against your back. Mutually-incompatible with 'quick access'.
- Casual shooting around town, in safer areas - a shoulder bag allows for far more rapid access than a backpack, so that you don't have to put it down every time you want to shoot, better manoeuvrability on public transport, in crowded areas, narrow laneways, etc., and a far lower likelihood of being stopped from entering stores, shopping centres, etc. than when wearing a large backpack. Doesn't carry as much gear as a backpack (at least not comfortably)
Multiple configurations for each situation may be needed, depending on exactly what you need to carry (tripods/monopods, tripod heads, long telephotos, UWAs, etc.).
