I think you already posted about that video earlier - did you forget that?
And the video is from one out of 100’s YouTubers with an opinion.
You switch around and mix as you see fit.
Be aware that Plasma and Gnome may have conflicting services - most prominently Gnome keyring and KDE Wallet.
You may also face strange issues with incompatible theming.
Other strange things may happen if mix Gnome desktop and Plasma desktop but Qt and GTK as toolkit does not conflict but getting a consistent theming is difficult.