Any light single is more than capable of negotiating the BC mountains. It is not the airplane that determines the outcome. It is the pilot. I put a ton of hours in Super Cubs, not XCubs,
flying into unimproved strips and gravel bars all over the province.
Pick your favorite. Plan some short hops between established airports. Watch the weather and follow the recommendations above. Experience and planning. No substitute. When you become proficient at valley flying in good weather, you can start planning some trips that require going over, not around, mountains. Keep them short and in good weather. Stay away from IFR until you have mastered VFR nav in the mountains.
FYI;
FL is reserved for designated airspace. In North America, FL is above 18000 feet.
Not FL06. 6000 feet.
Not FL12. 12000 feet.
Important distinction.
What is Flight Level?