As the holder of a Private Pilot certificate, you can fly any airplane with a gross weight up to 12,500 pounds. That means you can legally jump into any airplane as long as you meet the currency requirements established by the FAA. But would it be smart to simply jump in and go? The answer is, of course, a resounding no! But unfortunately some pilots do, producing an accident record for newly transitioned pilots that is less than desirable.
Although you can fly a long list of airplane types legally, insurance companies put much stricter limits on pilot experience. In many cases underwriters require several hours of dual instruction in a particular type of airplane before they will cover you. So unless you want to fly uninsured, you wouldn’t transition to a new airplane model without the assistance of an instructor who has time in that particular type.