I view bags as several different sets of tools - the bags I use to transport gear - particularly in modern jet airplanes - are distinctly different from the bags, back packs I prefer to use to carry gear when in the field or workshop. I wish I could use the same bag in both situations, but long experience has taught me otherwise.
Travel bags, for me at least, neede to be able to carry 2 or three bodies and 3-5 lenses( one of which may be a large tele) + filters, + maybe a speedlight and radio transmittter to trigger the speedlite, + a reflector or a diffuser of some type. This is more gear than I will probably need for a specific task during the day ( typically about 45 pounds ) , so I prefer to use a smaller back pack to just carry the bare minimum of what I need during the day - but not large enough for international travel.
I have tried to resolve this conflict many, many times over the years, and find I keep coming back to this conclusion - I need a travel bag and a lighter shooting backpack or messenger bag.
I would prefer a roller bag to travel with, but since I frequently end up in smaller commuter jets, I need a bag that will fit in the smaller overhead bins and I don't want to gate check my gear ever. So I wear it or carry it, rather than roll it.
For air travel I usually use a Gura Gear 25 liter or 30 liter Kibokobag - I have many others I have used over the years, but I keep returning to the kiboko for travel. It is deep enough for a 1Series body, not too heavy empty, very well made, almost indestructable, and well padded. Mine has travelled a lot.
For a day bag I usually throw a few items into a medium sized Osprey backback - nothing about the Osprey screams camera gear, it is durable and sturdy and fits well with a good belt if needed. If I am going to be in a Zodiac or around water, I may simply use a medium sized dry bag to carry a camera and lens or two. I usually also bring a Kinesis camera bag - a very water resistant, padded, zips shut bag for a DSLR body + mounted lens.
I use lens wraps in the Osprey to help protect gear.
About tripods - I always say I want the smallest, lightest possible tripod to pack around and then when I get ready to photograph stars or moving water or whatever, I want the largest, heaviest, most sturdy, strongest, most stable platform I can afford. Needless to say, I cannot get everything I want in a single tripod - so I have several, for different tasks. Heavier is better all things considered, except carrying. You can always hire a porter.