I think your Iceburg roses is a doable idea and would look quite nice. You have barely enough room , but just enough in regards to the width. ( in the photo below the planter is about 20 inches wide ) I live in Northern California and find that I need to routinely apply a systemic fungicide once every 4 weeks [April thru Sept] to battle black spot. I use Bayer 3 in 1 fertilizer/ pesticide/ fungicide ( comes in a granular form in a blue bottle ) This keeps the roses almost black spot free and blooming until Christmas day. From California Gardening I have never had any luck with training a bougainvillea to cascade downward. Their woody stems want to grow upward . In my experience I would say that you will have a challenge in maintaining a cascading / prostrate bougainvillea. I do ADORE bougainvilleas though !! I find them relatively low maintenance in comparison to other vines, especially roses. They require little to no water once established and bloom their hearts out from May to the first few hard frosts . They are thorny, but I only need to prune mine once a year - after the winter season to cull out any dead wood, and then sporadically during the growing season to keep a wayward branch in bounds.

I have Janice Kellogg here, and it does reasonably well. It can have good-sized flowers when it isn't being baked to a crisp in our summers. It is definitely NOT a floribunda in flowering habit. The plant can get tall. The flowers are a burgundy red in color and are old-fashioned in form. It is pretty. That said, however, I did see it also in Point Defiance Park in Tacoma, WA. It looked good there, but it was one of the few in their garden that had rust. If rust is a problem in your area, keep your eyes open on this one.

6 x 6 -- IN MY EXPERIENCE -- should be fine. Tee-Pee/Tripod. Three sturdy poles, preferrably wired together at the top. Long canes can wind around it. You don't need this for G.C., but maybe it would be good for Abe. Some use sturdy wooden poles, some use rebar, some use those green poles they sell at nurseries. See link for another idea. This idea from the Sacramento City Cemetery should also should work for Abe Darby. You might call this a "girdle" made of sturdy hardware cloth. Use the green-coated kind, and you barely see it. You know -- I would suggest that you might take a day trip to the Sacramento City Cemetery, and see some of the things they've done there, with big roses. It's getting close to my favorite time of the year there anyhow. Jeri Here is a link that might be useful:

Where in Zone 9 Central California are you? The sun intensity and the heat levels in most of California (and the West, in general) are too great this time of year to spray ANYTHING other than water. It doesn't matter whether you sprayed at dusk or the middle of the night. Neem is an oil. Once applied to a surface, it remains until it is washed off or eventually wears off. Brilliant sun and any real heat can easily cook the foliage and new, soft growth when treated with any oil. DON'T SPRAY ANYTHING. PERIOD. Keep them watered appropriately for the heat, wind, sun levels and drainage you have. If you want to fertilize, then follow the instructions on the label of whatever you decide to use. Believe it or not, you really don't HAVE to fertilize. I grow several hundred containerized roses here in Zone 9b on the Central California Coast between Santa Barbara and San Luis Obispo and I don't usually fertilize. I simply water. I don't generally have disease issues and if any start, I pay attention to the water. MOST roses can be forced to contract fungal issues if they experience sufficient water stress. If rust or mildew starts, I increase the water and it most often stops. To get slower things started, such as own root Teas and Tea Noisettes, I occasionally use All Purpose water soluble Miracle Gro or Vigoro, which is very similar and less expensive. I will sometimes use that weakly, weekly (instead of a tablespoon per gallon, I use a teaspoon per gallon and instead of every two weeks, I will use it weekly) to get things started, but not on a regular schedule. And, I NEVER use any fungicides nor pesticides on any of my plants. If a variety or one of my seedlings isn't healthy here in my conditions and the way I garden, out it goes. If insects appear, so do predatory insects and birds. Just keep your Icebergs watered and quit over dosing their foliage with applied products. Once they become established and are allowed to grow, the most common problem they experience is mildew on the peduncles and flower stems when that is an issue. Otherwise, unless overly pruned, they are pretty healthy in California. They are all over town here and most are watered by the lawn sprinklers and public planting sprinklers and they are clean, healthy and full of flowers.