it depends on who you ask, their expectations (do they run and require hardware acceleration apps, games etc?) and on what hardware.

beefing up the disk space and ram will take you far. you will be watching yt videos using the pop out window function, dragged to full screen (within vm borders) since "full screen". the virtualization daemon restricts a vm from owning the screen by default to avoid an imposter process from emulating the whole desktop etc.

the most delay i notice is waiting for an app qube to start up (takes ~5-10 sec for me) so pretty fast considering imo, and once it's running, i find the performance comparable to running on bare metal. i don't notice much if any difference in performance, but this is very much hardware dependent

it's pretty wild. xen shared memory is very effecient so most virtualized apps feel like they are run natively. you won't be running games that require hardware acceleration though.

i typically have 5-7 qubes running at once with at least 3 vpns, multiple apps open per qube, mutiple browsers with lots of tabs on a laptop with 32GB ram with no significant performance issues at all.

there's good info here to scan:

https://www.qubes-os.org/faq/#can-i-run-applications-like-games-which-require-hardware-acceleration