A Guide to Position Designation and Investigation Type

Hi, I have a questions regarding the investigation part.
I recently accepted a Background Investigator position
and was told I would need a security clearance. I thinks its
just confidential level but im not sure. For this level,
how far back will they investigate? and what avenues
do they use to do their investigation? do they have access
to looking into like text messages, emails, internet history or
like access to my icloud? or laptop or phone hard drive? Social media?
I also recently passed a level 2 background check, is it similar? do they have access
to medical information or history?