Please define GPU intensive. Using a gpu for video decoding can mean smaller battery usage in some cases.
Also it is not only about doing these tasks at a time, but if you need to shut down to be able to start another VM context because they can't be used concurrently it makes it very tedious user experience.
A normal qubes user workflow doing all your gpu requiring stuff in a single appvm-- you're not forced into isolation that doesn't work for you.
But you're also not running qubes if minimizing battery usage is a high priority for you.
As far as the tedium, perhaps a little, but bringing up a terminal on a non-currently-running app vm takes about 5 seconds for me, so it's faster than you might expect.
I think in general my view is that qubes has serious operating costs but they are much less than I anticipated.
And whats the real alternative? It's still better than carrying 5 laptops in terms of ease and usability.
We live in a world where browsers are constantly required but where their probably hasn't been a single day since their initial releases where Chrome and Firefox were without a RCE vulnerability (though often not a publicly known one).
USB-C PD has made laptop battery life less of an issue than it used to be, because carrying around extra battery life with external batteries is so easy. I typically carry one or two of these in my backpack: https://iniushop.com/products/iniu-b64-140w-27-000mah-fast-c...
That's enough for hours of intensive usage on my laptop, like running nodes and compiling stuff. And as you know, I run Qubes too!
I originally got an external battery when I went to Ukraine while Russia was trying to destroy the electricity grid; I got the largest battery I could legally carry on a plane (typically 100Wh is the limit). I ended up liking them enough to buy a few more.
Also it is not only about doing these tasks at a time, but if you need to shut down to be able to start another VM context because they can't be used concurrently it makes it very tedious user experience.