Should I delete plasma5-theme-sweet-full-git?

[nepti]

I advise you not to remove plasma5-themes-sweet-full-git. Because as you have correctly recognized, you would also have to remove garuda-dr460nized with all other dependencies.
If you still want to try, take a look here:

How to un-Dr460nize KDE

Garuda Linux is well-known for the bold visual style of the Dr460nized KDE spin, famously beloved by many of our community members and envied by other distros. Still, occasionally we have users who want to use KDE with all the amazing stuff Garuda Linux has to offer, but would prefer a desktop theme which is a bit more tame. Once KDE has been Dr460nized, however, it can be tricky to wrestle it back into a subdued state. This is because the garuda-dr460nized package, which provides the theme, is…

Another option would be to install “Garuda Linux KDE lite” and then only change/add what you want.

@aeskamrukh

I thought about changing their installation reason from “[…] as a dependency” to “explicitly installed” on Octopi

This does nothing, it only changes the installation reason and not the dependencies. If worst comes to worst, you will brick your system.