In this modern age, we have little privacy as it is, so you might as well keep your Google Account safe. Google allows apps and game makers to let you sign in with your Google Account. Apparently, Google has a strict policy about how services use your data, but it's a good idea to rid of apps and games that you don't use anymore.
There are different levels of access that apps can be given to your Google Account. Some apps may require a deeper level of access to your data, however, others don't need to have the capability to change your password.
Full Account access is where the app developer has complete access to your account. This even includes changing your password, deleting your account and sending money through Google Pay. They'd be able to access all your web searches, things you've watched on YouTube and other account activity. In short, no third-party app should have this level of permission.
Some apps may ask for read and write access. For example, a third-party email app may need to have access to read, send and delete your emails. If the service is trustworthy, then you should be good to go.
Other apps ask for your basic information. This is where you're connected to the sign-in feature. This usually includes your email address and name. Whatever is shown on your Google personal info page is what is shared with the third-party apps. This permission is the usual kind required by apps and games. If they need something more than this, you may want to find out why.
You may want to visit the permissions on both PC and mobile as the permissions may come up differently on the two devices.
You should do this for any apps you no longer use.