Before this starts to sound like Goldilocks, I must hasten to add that I am writing about a Lowepro product - a bag designed for mirror-less camera systems and the averae tourist user. Whether you use it for bear-hunting or porridge-stealing is your own affair.
The Lowepro m-Trekker SH 150
is a shoulder bag designed for a mirror-less body plus one or two of the smaller lenses and a few of the smaller accessoties that one would use on a day's travel.
Note the silencer tabs for the velcro and the little card pouch concealed under them. Also note the slim but strong padding in the compartment - your camera and optics are safe in a crowd.
If this all sounds like a little deal...the small bowl of porridge...consider what the average photographic day on holiday is:
a. Up in the morning and check that the batteries are ready. This argues that you have remebered to bring the charger with you - and the plural of battery means that you'll not run out of electricity at noontime. So you won't need to haul the charger with you in the bag during the day and try to find a power point in the hawker's bazaar. Plan ahead.
b. You'll either have one zoom on the camera for the whole trip or on on and one off in the bag. Your choice whether you change lenses while the natives are winnowing grain upwind of you.
c. Take a spare card. Change it every now and then. Let the GPS , EXIF, and computer at home come to an arrangement of what you took, where, and when. Or keep a notebook.
d. Pack a Gorilla Pod or something similar to hold your camera when you take selfies. Then don't take selfies...but use the Pod to hold the camera for steady landscapes.
e. It will rain at some point of the day. If you're in Singapore or Queensland, it could be all
day. Put the camera into the bag and get in out of the rain - the locals are doing so because they know the difference between being wet and being dry, and you could learn from them.
f. As the day goes on you will be getting older and that bag will be getting heavier. If you start the day with a heavy one you will feel like death by 3:00. Be nice to yourself and pack lightly. Like Kipling's cavalryman, if you lose an ounce of weight you go a mile further.
g. Wind the bag's strap around yourself so that it is hard to snatch off you. Keep the sturdy clips fastened shut. Same with your wallet - but when it comes to paying for the drinks open that on a friendly basis.
Don't try to stand out from the crowd. They all know you're a tourist anyway - just travel in patrol order with a scout, wingers, and tail man. And keep your eyes and ears open.
And have fun*.
* Fun is getting back to the hotel with the gear you took out in the morning plus images. Scalps are optional.