What guidance do you actually want?
If you don't use the apps, disable them (I'm assuming they are installed as system apps and so you can't uninstall them). You'll break a lot of stuff if you disable Google Play Services, if it even lets you do that, so leave that one alone unless you really know what you are doing (you will never launch it, but it does its work in the background). But other stuff like Google's music apps, video apps (YouTube), this that and the other you can disable with no consequences.
If you want advice on a specific app, tell us which one.
If you just want to know why they are there, it's probably because of a condition that Google impose on manufacturers: if a manufacturer wants to offer things like the Play Store or Maps they have to pre-install a bunch of other things as well. Some day maybe the competition authorities will look into this, but they have more urgent issues of that sort with all of the tech companies (Google included). But as I say, if you don't use them or anything that depends on them then just disable them and forget about it.