I get the feeling that 90% of the check is if you are signed into a Google account, otherwise you're going to click some images. I've noticed this a lot of incognito mode where I will almost always have to do a captcha.
I don't think so. When I was traveling in Malaysia a few months ago I was always signed into my Google account, but constantly needed to fill in captchas and even got suspended from Google Scholar for a few hours for "suspicious traffic".