If you're overriding the default permissions.. Flatpaks attempt to sandbox applications not built to work in a sandbox so the packages usually come with lots of holes prepunched that you probably can close without issues.
Standard Debian packages have access to things like your home folder and other things that can be accessed without superuser level access. If you're not okay with that, don't install it.
If a flatpak package is available, it can have it's permissions controlled by Flatseal, allowing you to restrict Spotify's permissions.
On Linux, all unsandboxed apps are allowed to do anything your user account can do (without sudo) - there is no permission model. You could use Flatpaks but they're not perfect, likely would require customizing with Flatseal.
Not answering your question directly but have you heard of Nuclear Music Player? It searches the Spotify API for track names and plays them from Youtube.