Choosing Best Laptops

Battery times vary according to use by up to 10X. And gaming can take a 10 hour rated laptop down to 1 hour.

This means that for you the technology for a gaming laptop with all day battery isn't here yet.

May be a few more years to get there.

streaming video will drain a battery pretty quickly. As Bob says, running gaming on battery on a laptop, you'll be lucky to get more than a couple of hours run time.

Some of the new thin machines from Acer and Dell claim a long battery life but you'd need to find a detailed benchmark review to verify the claims.

Depending what else you want to do with the machine, some laptops come with dual graphics chips, Asus is one that springs to mind, a lower performance chip for mundane stuff and a higher performance one for more intensive video and gaming, though whether that would include the modern intensive games would be a question to ask.

There are a few with reasonable battery life:
https://www.lifewire.com/best-gaming-laptops-for-battery-life-4686937
Or maybe this:
"If you can give up some performance for battery life, getting a cheaper model might help you out. The Dell Inspiron 15 7000 Gaming, starting at $949 with a GTX 1060 Max-Q, is a truly affordable system, way under budget. More important, it ran for 7 hours and 5 minutes on our test, which is long for most gaming notebooks."

I'd research batteries, easily removable, and those with 6 cells and longer rated run times first, see which laptops can use them and work backwards from there.

https://wiki.ezvid.com/best-long-battery-laptops

If you intend to also dual boot with Linux, avoid Lenovo Yoga and those called "Signature Edition" ones.