I am a healthy 25 year old. Internal medicine or family practice doctors for pcp?

Either. Is qualified to provide care. Which you prefer may depend more on interaction and rapport you develop with your provider.
Doesn't matter . You can choose either. It won't matter if you're otherwise healthy.
Either. Either type of doctor is well-trained to provide your general health care.
Either. Depends. . Rather than whether a doctor is family practitioner or an internist, what is more important is that you find a physician with whom you can connect and develop a trusting professional relationship so that you won't hesitate to share any health concern or ask any question . Good luck.