If in doubt about anything just post on the forums and ask to get an answer. A general rule of thumb is if you don't enable anything under the 'Cleaner -> Windows (tab) -> Advanced' area you'll be alright - the only two exceptions being 'Custom files and folders' and 'Wipe Free Space' should you have the need to use them.
on each of those (or any) entries, you can right click and select Analyse and it will show you exactly what will be cleaned.
from the list of files given, you can then decide if it will adversely effect you.
Unless it's something automatically cleaned from the registry such as MRU, then it won't reveal anything.