I might be busy in the next 2-3 weeks so I will update you in a bit.
Awesome thank you for your feedback! Here's mine:
I decided to buy a Raspberry Pi 3 B+ because my Raspberry Pi Zero W wasn't able to handle Raspbian+Chromium (kept CPU at 100%) - I was running a "game" at 800x480 and with 3 textboxes & 2 small 5FPS sprites going on at an astounding 1FPS even with WebGL active (in the game as well as Chromium).
However, when running the Arora browser from NOOBS I got a significant improvement with an average of 7 FPS.
In any case this isn't close to what I need (at least 20FPS) - so I hope the Pi 3 will help. Waiting for it to arrive, I'll share all the details once I get my hands on it!