[option_greek]

Use private mode exclusively. You will start getting into the captcha hell in a day or two.

[srg0]

I configured Firefox to delete all cookies on exit, except few whitelisted sites. So most of the time I have to accept Google privacy policy if I search there. Other than that, I never got into the captcha hell when trying to do a Google Search.

There are some sites I can't login at all unless I change the browser. SoundCloud is one of them.

[option_greek]

Could be that IP Address/ISP reputation is also a factor for the variation in results.