I've been flying Spits as my main ride here and in AW for over 14 years. The Spits IX, VIII and XVI have advantages that can be exploited against any plane in the plane set. It's up to you to learn what those advantages are and learn to exploit them.
The Spit's VIII and XVI in particular, while not being the top plane in any category, are near the top in virtually every category. Pick one; Speed, climb, lethality, turning ability, acceleration, roll rate (more so with the XVI than the VIII), etc.
Either of these planes can make quick work of an La (5 or 7) or an F4U of any variety if flown right. Your decision to run from these match-ups only means you haven't fought them enough to learn your own strengths and their weaknesses. More than any other plane these Spits can transition from BnZ to E fighting to stall fighting and back with equal ease and it's why they are often referred to as "easy mode". They can fight any type of fight required and are quite forgiving if you really mess up.
In conclusion, there's no plane in the set I'd run from or avoid a fight with in the Spit VIII and if that's what you're planning on doing you're going to greatly hamper your development and understanding of your aircraft. The only situation that you have to be wary of is a high speed BnZ type coupled with a tighter turner two on one aganist you. The BnZer will get you to turn and the turner will try to eat you up. Other than that two and three on ones shouldn't be a huge problem if you keep your SA up.
Fly, fight, die, learn, have fun.