On browser extensions, uBlock Origin has come a long way that it basically also does what other privacy extensions provide. Simplifying your content/tracking blockers can actually make your browsing more secure, as well as make your fingerprint less unique. I’m still a bit of a sucker and have Privacy Badger installed, but will probably let go of it as well once I’m comfortable enough. Over the years I’ve had Disconnect, ClearURLs, and Decentraleyes alongside uBO.
Unfortunately it depends on the individual, so no one can really answer your question but yourself. For me, I draw the line when it personally becomes burdensome to maintain something. For example, I use Bitwarden to manage all my passwords, but I don’t trust myself enough to host and maintain a server and keep it online/secure, so I use their hosted service. I use google drive to store some miscellaneous stuff because of the free 15GB storage, but I don’t store any private files (personal photos, documents, etc.). I use ProtonDrive for more important stuff, and for very confidential files, I encrypt them first. I use google maps for navigation because of reliability and accuracy, but I use a separate google account for it. I know that doesn’t do much, but it keeps some level of separation for me personally. I still maintain a facebook account (although I barely use it) because of family, but I still use a facebook container on firefox and don’t use the mobile app. That plus all the privacy extensions.
The main thing is that it doesn’t have to be black or white. You don’t have to go full hermit, and at the same time you don’t need to fully embed yourself into the google ecosystem. Just do what you can and what you are comfortable with. As they say, don’t let perfect be the enemy of good.
I can share a bit and confirm your expectations about the locale part. I moved to a different country and didn’t need to change my locale for a couple of months until I was forced to because some apps I needed (banking, transit, etc.) weren’t available in the app store unless I changed it. Other than that I didn’t seem to have any major issues. I believe subscriptions can also be tied to your method of payment (i.e. which country your credit card was issued) rather than locale, but that will vary depending on the app.
Ghostery used to sell (or just send back) user data to advertisers. While it was opt-in, that isn’t really a good look for a privacy tool. I stopped using it when that news broke out long ago, but I think now they are also showing ads of their own(?). Either way, uBO does almost everything now. I have Decentraleyes too, along with ClearURLs, and Privacy Badger (which supposedly is redundant to uBO now too).
10-15 minute brownbag sessions. People won’t be bothered to read privacy guides links you send them. Bribe them with food. Try to get them all together somewhere with the promise of some snacks/drinks then have an interactive session about what you want to discuss. Don’t make it a lecture, make it like a casual conversation. Pick a topic and start with a real life event that happened that may directly affect them (i.e. the recent ssn breach). That will get them engaged.