I like the Aqueon bettabow/minibow tanks I don't use the divider in mine. I just use them for 1 betta.
I don't know if this was answered yet because I didn't read the whole post yet. You may want to think about putting a sponge pre filter on the intake tube. This will stop delicate fins from being sucked in if they get lazy and decide to go sit by the bottom of the tube.
I use Aquaclear filter foam which is ugly in one tank. (It works GREAT but is far from attractive, and very obviously WHITE!!!!!)The other one I use the Fluval Edge pre filter sponges. The fluval sponges already have a round hole cut in them already and you can slide it right up onto the filter intake.
I don't know if they changed the sizes of the fluval edge hole cut out now, but I had to put a small ring of airline tube in my more recent sponge to keep it on my filter. (I cut a ring of it just big enough to barely go around the intake tube and slid it down into the bottom of the sponge. It just pops on then and stays secure.) They are black and look nice on the filter though. My fish like to slap themselves on the side of the fluval sponge and sleep. (There is just enough suction to hold them there.) I might just have lazy bettas though.
Here is a picture of what i'm talking about, It will help hold a nicer beneficial bacteria colony in your tank too when you change filter cartridges.
You can use pretty much any filter sponge medium you want to btw just cut an x in a piece of the foam/sponge and jam it on the intake. I just like how this one looks the best out of what i've used.
You can use a piece of nylons too... but i've found it starts to look a little funky after a while so I don't use them anymore.
Just wanted to share. If this was answered already i'm sorry.
Edited to add: The stuff that came with the tanks is Aqueon Betta food, I use it, my fish love it. Each betta is a bit different though and may be a picky eater or could have a small mouth. New Life spectrum is a good brand of food too, and is recommended here a lot.
Someone told me that you can jam a piece of sponge inside the filter intake too and it will help to baffle the output of the filter if your fish is having trouble. I can't say if this works or not though. Maybe someone who has tried it can say if it works or not.
You can get creative on backgrounds. They sell a good selection of backgrounds at the pet store. I have one that is freshwater plants. I've used a piece of crafting felt for a while. In some fish forums people say Sea blue or black backgrounds bring out the tank better then a white background. Use what you like to look at though, and what compliments your tank decorations. :) Your tanks are nice. :) Pretty bettas too!