This is actually a very broad question, and I'm not 100% sure it is best suited here. That said, I'll try an answer:
Sports Stack Exchange has this question on sail choice for sailboarding, which actually led me to this useful page on poolewindsurfing.co.uk.
They have an excel spreadsheet which helps you calculate sizes, and their example for a 68kg sailor agrees broadly with my experience:
- Minimum size beginner board: Volume 172, Width 82, Length 297
- Ideal first shortboard: Volume 118, Width 74, Length 268
Initially you need volume to help you stand and balance. When you get better, you can use a semi-sinker or even a sinker (a board which will not support you by buoyancy alone but that requires speed)
A freeride board is much more manoeuvrable than a long board, but a long board can be much faster. And a board with long hard chines can make long distances less tiring, but will not be able to turn as rapidly. (I remember once watching a guy practicing for the world speed record out in the Falklands. His board was not easily turned, so at the end of his 2 mile beat he would simply fall in, manually cross the sail over and then restart in the opposite direction)
In the early stages, your sail/board combination needs to be able to be uphauled. Once you can start from beach or water without uphauling, you have much greater flexibility in sail size, board type etc and can use a much smaller board and much larger sail.
You also want to look at fins, centreboard and footstrap placement.These can be more suited to flat water and speed, or choppy water, waves and jumps. Also, for tricks you will want to look at light boards and possibly short sails (for loops etc)
tl:dr Like I said, most of your question is incredibly broad, and probably not worth worrying about at this stage. Just get an intermediate board with maybe a 4m^2 sail and it should do just fine.