The different models definitely do not produce the same output and some weather conditions are extremely difficult to predict with any accuracy (especially rain). Even the "current" conditions are often very different depending on the model since they rarely use actual observations... and even if they did the next city block over could be totally different).

Which one is the most accurate depends on your location (in particular, your latitude, proximity to the ocean, nearby mountains, etc).

Even little things like standing near (not even under) a tree can drastically alter your air temperature - because trees raise the humidity of the air around them and a slight humidity change has a drastic effect on temperature.

Apple most likely uses multiple models.