Should I use Qubes?

[unman]

Kind of true.
If one uses laptop with CPU that is not recent Intel 11-12Gen then it’s quite possible that even Youtube will be quite laggy playing basic 1080p@60fps videos. In Kubuntu it will work flawlessly even in 5 players simultaneously due to hardware acceleration that is not available to qubes in Qubes OS.
Other stuff is about twice slower to my estimation, that is not a lot.

Not so in my experience.
I dont have reports of laggy YouTube even on x230 - there can be
issues over Tor but that’s a separate issue.
Nor do I see “other stuff” (what?) running “twice slower”, although
perhaps I dont understand what you mean by this. Do you mean that music
players run at half speed? That editing is half the speed?
Even 10 year old CPU provide a reasonable Qubes experience, and once
qubes are started there’s minimal slow down in ordinary use (in my
experience).

These judgements will depend on what applications you are
running, and how you manage your qubes.

I never presume to speak for the Qubes team. When I comment in the Forum or in the mailing lists I speak for myself.