If you want to learn to cut bowls.... Buy a book called "Wooden Bowls from the scroll saw" written by Carole Rothman. I got my copy from Fox Chapel Publishing and it costs $19.95. You may be able to find a copy at a local book store or order it on line or at least try the local library.
I guess that it is possible to cut a bowl that aligns correctly right off of the saw but, I've never done it!
There is always going to be a lot of sanding to be done.
It is a question of the thickness of the wood, the kerf of the saw blade and the correct angle to the dangle of the saw table. (or head tilt in some cases)
I have made about 12 or more bowls and quite a few vases and mugs and always get some off-set between segments but, it is not to worry, it can be sanded out. (the less sanding, the better of course but.....)
When you start to glue up the segments, don't try to align the edges, center them with as equal over hang all around and pay some attention to aligning the grain and press two segments at a time together until the glue dries. Then glue another segment (or set of segments) to the first set.
Be sure to sand the inside nice and smooth BEFORE gluing the bottom on then do the sanding on the out side after the bottom is on and the glue is dry.
Hope this helps some.
Rog