Here's some context for the questions.
I installed Windows 10 on my first HDD /sda 128GB.
I installed Linux Ubuntu 18.10 on my second HDD /sdb2 ~150GB
I also previously partitioned that second HDD an NTFS ~700GB on /sdb1 (so that W10 can read it).
That's roughly what I did and was happy with this dual boot setup which was pretty easy to do (once the right tools in hand).
The VM Argument
I hear dual boot is the "the 5-minute alt-tab". It takes time to go from one to the other. Why not have a VM running? That's exactly what I do at work. I have a W10 host and use VirtualBox to run a linux VM. I had some problems at first, then fine-tuned it to run ok alongside the host.
But it's not perfect.
At home I have two screens. really the ideal would be to have both OSes running simultaneously, one on each screen. But we're back at VM, and virtualization and everything it entails... Are we not?
Hypervisor Type-1 / Bare-metal
I just learned about that today. Seems pretty nifty, but also has drawbacks: accessing the GPU and stuff like that. Like I said, I don't know much about.
Is Hypervisor a no-go with Nvidia GPU, given that my objective is to be able to game like I want on Windows, but still have my Linux not far away?
Does it have other drawbacks(I think I read something about PCIe), incompatibility issues for virtualizing certain hardware, driver issues and whatnot?
VirtualBox "Save State"
There are so many uncertainties. And my setup is already done and functioning. I don't want to go back to reinstalling W10 and having warnings, incompatibilities, issues etc. because I'm trying to run it under hypervisor and it believes it's a root-kit or what... I just want to quickly (if not instantaneously) switch between the two OSes.
I continued my reasoning like that, the epiphany is soon.
The problem with shutting down one OS or the other is that everything disappears. So there's not only the time to shutdown and time to boot the other, there's also the time to relaunch every service, relaunch every app, get back to the point I was at before shutdown etc. just like if I didn't shutdown the OS! Is there a way to...
Bingo! VirtualBox does just that with the save state feature. That's awesome. I spent some time searching on windows states: hibernate and fast boot are close but not what I want. The infamous reopen apps on boot or whatever doesn't seem to be what I want either.
Is there this basic feature on Windows 10 and Ubuntu 18.10 specifically to save the state of the machine at any given point (simply dump the ram on the hard drive, right?) and then be able to load that state back when you boot (just put the data on the hard drive back into the ram, no?)?
That would be as close as what I can get without virtualizing anything...
Are there issues, in late 2018, running W10 on Hypervisor? Is there a free solution? Does it have any drawbacks? Will it impede on performance due to the virtualization? How much? Are there any necessary hardware requirements for it to work? Bottlenecks?
Is there any way (software, native solution or whatever, command lines, a bat and shell script for a peculiar way of shutting down and booting....) to save the state of the OS (W10 and Ubuntu18.10) before shutdown and load that state back up on boot?
Given the context, I believe this may not be subjective: what's the best (i.e. most efficient) way to run Windows 10 and Linux side-by-side (on the same machine) with the least downtime between access to one and the other and no lagging/ramming issues or bugs/graphical glitches etc.?
PS: Don't hesitate if more details needed to properly answer.
Don't hesitate to not moderate my question, I like context (I believe this is relevant and my question still remains straightforward with straightforward answers, albeit substantially long, by necessity, and I believe this will also be good for future reference for other users pondering on the same questions who will recognize being in this exact same situation).
Of course, if you think you can make my questions clearer without stripping information as to the situation I'm in, don't hesitate.
Don't hesitate to bring this forward as a duplicate if there's already good walls of text out there that answer my specific issues :)
I'm interested in any material you bring forth, I like reading.