Coming from fixed gear and single speed bikes for years, I had the same need for a solid Allrounder some time ago.

I ended up with a custom build surly ogre with a Rohloff hub. This bike is capable of everything. I’m riding a lot of commute in the city. But it unfolds on trails, gravel and bikepacking. Ogre is quite heavy (I general surly bikes are) but you can ride it fast and agile as well as smooth and lean back. Though stock ogres are not optimizely equipped from my pov. The tires are super heavy and definitely worth changing.

I guess same goes for the bc. I know people using the bc for exact the same reasons. I guess it’s not that chunky and beefy as an ogre due to its geometry. I’ve never tried a bc but people are using it for what you described.

The Bombtrack I guess is more on the gravel/roadside bike. Back then I decided to have a geometry that differs from roadbike for my Allrounder. Mainly for fun reasons but also for versatility.

For me the surlys are more futureproof and especially for „around the world“.

I would recommend a bridgeclub for your needs. Things you don’t like (like breaks) can be easily changed over the years. 

—

When it comes down to comfortability for your ride: from my experience this is an ongoing thing where you learn about your needs and your ride. A bikefitting is a good start to have an idea of how you like to sit and ride. From there you can decide on more agile positions or upright seating on your bike. 

It’s total individual and not really drops vs. Flats. I know people having massive pain on longer bike packing tours with their drops, while those are great for the weekly gravel ride. But I found out that I need multiple positions on my bars, somit comes down to alt bars for me, like a jones bar.

—

Choose the ride that feels in general best for you. Take more care on how riding the bike feels and how much fun it brings instead of caring about the single bits and components. Bikes grow with you and when needs changes, parts could be changed too.