I've been using DuckDuckGo as my default. I mostly only use google for news search now. No complaints.
duckduckgo works really well. For some topics google is better, but for 95% ddg do the job as a day to day standard search engine. And those times you need google, it is very simple just to add !g bang to get the google search results. With ddg you get better privacy and dont end up in googles filter bubble. More should try it out.
Does it still affect you if you don't connect your FB account? I wouldn't think so
Advertisers can still figure out how who you are without linking an account. It may take them slightly longer, but the information is out there.