No problem, and luckily all your questions are easily answered. Cheetah is indeed a bot that does just that, scours the internet for text that is copied and pasted. When it detects a match, instead of flagging it, it gives you this message-

Hi! I am a robot. I just upvoted you! I found similar content that readers might be interested in:(link to the post with the same text).

If you are borrowing from your own blog on a regular basis all you have to do is send a message to cheetah that shows you own the other blog and you can be whitelisted so that cheetah ignores those posts coming from that site.Keep in mind, cheetah doesn't flag any of these posts, it just lets the reader know that this material is posted somewhere else online. The bot can't give any context to the situation, thats why we have actual people who run steemcleaners to look at every post before taking any action.

Unfortunately cheetah doesn't catch everything so you are correct, it IS a tremendous amount of effort for the volunteers of steemcleaners who spend their time googling chunks of text to find copied/spun material, doing reverse image searches on plagiarized photos, and using google translate to find all the foreign articles that cheetah cant find, etc..

As far as photos go, sure, if you took the photos on your post simply state that in the post. If you didn't take the photos you use in your post, just link to the source of where they came from. There plenty of sites out there like pixabay that have a ton of photos to use for free.

Steemcleaners generally won't police a few images in a post, even unsourced, so long as they aren't the entirety of the post. If, however, you are posting in the photography tab and trying to pass of photos as your own that are clearly not yours then you can expect a comment.