I always use piCore for low end and embedded.
http://www.tinycorelinux.net/ports.html
Based on Tinycore which was evolved from Damn Small Linux?
http://www.tinycorelinux.net/
There is a light X win for it, but I don't use it much, mostly CLI.
Good luck for OpenGL, accelerated HW stuff.
Not sure about a browser, good browsers tend to be big.
Hoping Kernel 4.8 might help with this.
Once a good browser and OpenGL runs on piCore I may end up ditching Raspbian.
Some HW stuff like the Pi camera is not too hard to get working.
There is very active development for piCore, most times the kernel is ahead of Raspbian.
You do need to know what you are doing, not a beginners OS, but the forum is very helpful if you get stuck, but read the Core book first.
Never tried it on a Pi3, it should really smoke.
There is not a lot apps for it, choices are limited to sometimes one.
Most apps can be recompiled for it, if it is useful it usually get added to the repo.
Uses a compressed file structure that is loaded into ram on boot.
Very fast and crash proof.
Not a kitchensink OS, more a handbasin and byo soap
It comes with micropython built in, just need to install busyboxhttpd server.
Really, really great for IoT out of the box.
For dedicated, one off use boxes, it is hard to beat.
Not so much a general purpose do everything OS, you end up installing lots of extra stuff. Very easy to backup the whole OS.
If I knew how to compile for Linux, this is the OS I would port to.
No code bloat, just fast, small and stable.
I routinely pull power on the OS, alway reboots fine.
Latest Raspbian is not playing nice with my new 16GB SDcards.
I have run piCore from 128MB SDcards with 60MB free
Cannot find smaller cards
Cards that stop working on Raspbian get recycled into piCore boxes.
Because it is so limited and there is not a lot of apps/libraries that can be installed I have had to learn things the hard way like basic LInux stuff Grep, Shell, Awk, Sed. For IoT this turned out to be useful.
Shell script running on 1GHz Cpu's is fast, sometimes need to throw in a bit of micropython.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges