What is the main advantage of choosing Fedora 34 over Debian 11 or vise versa during the Template Configuration stage of the OS installation?
Ex) since I use Ubuntu as one of the main Environments would Debian 11 have more advantage in this scenario for optimization and performance purposes?
Or will it give me the option to choose everytime I create a standalone VM? I mainly plan to have Windows 11, Kali Linux and Ubuntu as a standalone vm’s
Sincerely
They are different linux distros:
Arch is the spear head. Bleeding edge rolling release: You get all updates as fast as they are coded. Because of that, your system tends to break more often as mistakes happen.
Fedora tends to get updates relatively quickly. If you are using hardware that needs new drivers, this is a good option while being more stable than arch linux.
Debian tends to be very stable, as all updates (besides critical security updates) are battle prooven. On the other hand, you have to wait a long time for drivers or feature updates. Literally years in some cases.
Disclaimer: May contain opinion!
Ubuntu is based on debian. It is more loaded with “stuff” that many ppl find good as they do not have to configure or install much to get started. Other ppl find it to be bloated/configured the wrong way.
IMO debian is better in an appVM qube setting than ubuntu. In a standalone this boils down to: Personal preference and what your goals/tasks/workflows are.
You are using qubes now, so just experiment! You have unlimited qubes you can play with and find out what you like! 
Go for it!
Oh and another thing: Qubes really starts to shine with the dispVMs and AppVMs. Start how you like to do things, but with those features you have more control and security instead of using just a couple of standalones. This is just a can not a must of course.
Install default, and change on the fly then conclude yourself. It will be an amazing journey.
You wouldn’t want to use standalones in Qubes (thus meaning HVM) unless it’s impossible to use distros otherwise.
This means, sys qubes with dedicated hardware have to be HVM, as well as Windows qubes (standalone or template, search the forum)
Kali template is officially provided in qubes-community-templates-testing repository, and @unman provides many other templates beside Ubuntu .
If I’d want to use only standalones, I’d reconsider using Qubes, although it is better than running them in virtualbox-like environments.
If you ask why, you can read it here why PVH is more secure than HVM
Thanks for saving me so much time and much appreciate it
From the docs:
The standalone/template distinction and the HVM/PV/PVH distinctions are orthogonal.
You can and should use PVH virtualization mode for Standalone qubes. However, AppVMs are more secure and convenient, because they isolate the root filesystem and reset it every reboot, making persistent attacks harder.