I have two sling bags that I really like. They are made by Think Tank, the Turnstyle 10 and Turnstyle 5 (smaller). They are small, so you can't be burdened by excessive weight, you know when things get heaver after you have been carrying them for a while. Also very easy to use, just slide it around and open up, not like a pack you have to remove. I have had the larger one for about three years, and the smaller one for just over two years. I use the large one most all of the time, my KP lives in it with the 55-300 or DA 20-40 mounted on it. My DA 15 is always in it, and I can carry another small prime (up to my Tamron 90 macro), or a flash. I got the smaller one as a fathers day gift, at the time I also had a Sony a6000 that I used with it. I no longer have the Sony, but I used the bag on a trip to London in October when I knew I did not want to use the 55-300, I had the KP, DA 20-40, DA15, and F50 in the bag, it was perfect, I carried it all day everywhere for a week. There is also an attached rain cover that pulls out of the bottom that I used a few times. When we got on a train or bus all I had to do was slide it around to my chest. I packed it inside of a backpack for air travel so I could take other items like an ipad, magazines, power bank, snacks,,etc on the plane too, I have also done that with the Turnstyle 10. These bags do not have a tripod carrying method, maybe they have some type of add on for that, I have not checked. They do have videos of how to use these bags on the Think Tank web site. I am very happy with them, for my use they are just right.
Here are a couple of quick cell phone photos I just took.
This is the two bags showing the sized difference, the larger one of the two is what I use mostly. ThinkTank makes a larger sized bag also:
Here is the Turnstyle 10 opened to show my gear, you can't see another divider that has four filters in cases stashed behind it:
And here is the front pocket, spare batteries etc: