You can camp in those places. There is a map of the restricted areas at
http://www.lochlomond-trossachs.org/things-to-do/camping/go-wild/. Ben Venue is near to the restricted area around Loch Achray but there are plenty of places to go.
Many people (myself included) will be reluctant to share locations for overnight stops - as this prevents them from becoming over used. Try to choose an area that is sheltered, and with access to water. My advice is not to try to plan a specific spot, but select a general area and choose the precise location when you arrive there based on the conditions at the time. If there weather is poor then maybe a lower, more sheltered spot; of higher and more exposed if conditions are good/settled.
Remember that you'll need to protect yourself from midges as well as the weather.
If you have backpacking experience in the US, particularly temperate areas in the northern states, then I think you'll be fine. No bears here!