You will work yourself to death trying to flatten a board with one plane. You need at least two and possibly a third.
First you need something that will quickly take off rough, thick, shavings. I use a #6 with the blade ground to an eight inch radius.
Some people use a #40 scrub plane but that is too small for me. Some use a number 5 with the rounded blade.
But, the idea is the same. Make quick work of removing as much wood as possible in the shortest time with the least work.
Then you need to level out the slight dips and waves left by the first operation.
For this you need a jointer plane, either a #7 or a #8. This will allow you to flatten and level the board.
If you then plan to use a power planer then that is as far as you need to go. But, if you want to hand plane the finished board
then you will need a #4 that is finely tuned and super sharp to get that high sheen clean surface that is almost ready to finish.
So, it is really a 3 or 4 step process that requires different tools for each stage of the work.