"To peek" - means to have a sneaky look, or a quick glance at something.
"To peep" - means the same thing, but can also refer to a "peeping Tom".
"Peeping Tom" has a similar meaning to "voyeurism"
A person who derives sexual pleasure from secretly watching people undressing or engaging in sexual activity.
Therefore, If you want your meaning to be understood and not be taken, as a pervert (perv). Then use the word "peek".
Pervert (noun) - A person whose sexual behaviour is regarded as abnormal and unacceptable.
Hope this clarifies it for you.