Thinking of buying one for for small stuff for segmented bowls. I am talking about the bench top or portable, no room for a big one and don't have any dreams of doing furniture work,any one using one,if so would like to have one that is a good one.400 to 600 budget.
While this is a the top of your budget the Dewalt 735x is rated very high. Our club is looking into purchasing a Dewalt for use on smaller boards.
I don't have any personal experience with benchtop planers. You may find the wood magazine article useful on deciding which planer is the best for you.
Be sure to look at the minimum length requirement and the maximum width requirement before you buy. Mine is 7-1/2" minimum and 12-1/2" maximum, which leaves me with all the starting and ending rings to deal with on my Cole jaws or drum sander. It's hardly worth using on rings.
Thickness planer is good for prepping the stock prior to segmenting, but you will also need a jointer to make the stock square and true or you will have problems on down the line. A drum sander is nice for flattening rings but not critical. A homemade disc sander mounted on your headstock is an economical solution for sanding rings as well.
I have never ran a segmented ring through a planer. I have only used a planer to reduce stock down to thickness (+ a bit left for sanding). The stock is then cut into segments and rings are built.
You are correct that one needs to look at what your requirements will be as far as material size.
I did try it and several medium-sized rings went through okay but apparently the bottom side has to be pretty flat first. I had a ring explode inside the planer. I assume the first pinch roller cracked a glue joint, allowing an end to get into the blade, then it got exciting. I had to take the whole planer apart to clean busted pieces of segments out of the chip path.
I went back to my Cole jaws. Those work on all the rings in a project.
If you would like to build a sort of like planer but a thickness sander you can use your Lathe for that.
The lathe would spin the roller kind of like a spindle sander that has several lengths of spindle. I know you can buy a 9" and even make your own out of wood to any length you wish and have a platen under it so you can feed the wood into the platen and the spindle will sand it.
I am pretty sure there are several made ones on YouTube to watch.
I would like to suggest purchasing PORTER-CABLE PC305TP which is an affordable price benchtop planner. Its price is not more than $350 which is within your budget. When you make your segmented bowls, this benchtop planner will help you to maintain uniform thickness.