Betta in a community...
Okay, I am speaking from pure experience here, as I keep a male crowntail betta in a 15g tank with 10 kuhli loaches and 5 harlequin rasboras.
I do NOT recommend bettas as community fish, especially if you arent VERY familiar with bettas to the extreme. Many reasons this does and doesnt work out.
Every betta has their own personality, some can have tankmates, some can have a lot of tankmates, and others need to be completely solo. It takes a trained eye to pick out a betta that seems like it MIGHT be capable of getting along in a semi-community environment, then it takes trial and error finding out what if anything can be kept with the betta...of course this usually means something dies in which makes it a big risk on even trying. (Thankfully I have had no fish-loss to this, *knocks on wood*)
Bettas generally only prefer one small group of shoaling fish when in a community. My betta must be super special because he deals with not only the rasboras, but TEN loaches that love to constantly swim circles in the tank. (My betta actually seems like he prefers the loaches to the rasboras for whatever reasons.)
My betta is use to community living and has been for many months (previously housed with ADFs, otos, neons, snails...). Just because he is use to it, doesnt mean I dont watch him very carefully, because at any moment he can get mad and change his mind on community living. The other day he started to get mad at one particular rasbora that was trying to hang out in a plant the betta was heading to...and the betta flared (gills and all). The 2nd time, he flared and chased the rasbora for a second. Thankfully the stubborn rasbora gave him his space and all was okay...but it could have ended in a dead rasbora!!! And odd as it is that my betta is housable with others, I had put a ghost shrimp in the tank a couple of weeks ago, and a big one too!! In 2 days my betta killed it, dragged it out of the java fern, and ate the body. (He flared at the dead body inbetween bites...he is funny.) My betta's name is Lassie by the way, as he hadnt had a name for the longest time, and then when I housed him with rasboras he decided to herd them like a dog, so I named him Lassie! LOL
But yeah, its always a gamble and a fish can and eventually will get hurt. I am always on constant alert watching for behavioral signs that things are going to go wrong so that I can take action and get the betta out into his own tank away from harming my other fish. Now, in the past, I have had bettas that you couldnt house with ANYTHING, they were just that mean. Thankfully my betta nor other fish in that tank are showing any kinds of stress due to tankmates.
Some of the fish species that have been mentioned...I would avoid the angels due to their desire for a group and tank size. Gourami, in your tank, you could do a blue gourami safely, or the gold or opaline version. I do recommend a female though, as before I got mine I did some research and some males are just too much of a bully. For cories, I have always avoided panda cories because I have heard they were way too sensitive to water parameters and it scared me away...after I got use to having less than common cory breeds (julli and habrosus) I know now that the pandas wouldnt be that big of an issue. However, I do feel they are shyer than most cories and would say 6 of them is a better grouping. With the softer water and lower pH, have you looked into sparkling gourami? They are beautiful, small, shoaling, and even though a group of them, they would still stand out as a group of "focal" fish.
I had gotten my gourami as a "focal" fish... I dont advice it as they are so shy, even with floating plants and all their needs met. I think my gourami, named Ginger, is BEAUTIFUL, but if I knew what I see now, I would not do it over again with it as my focal fish.
I think you could do a blue ram from what I have researched and been told in your tank with the rasbora. I plan on adding a blue ram to my 29g in the coming weeks. I think blue rams are much prettier than any angel, gourami, or betta if given the right water parameters and temps to show their true color potential!!! (Same for any fish really, most dont like cherry barbs, but in my shoal of 9 I have some amazing red males!!)
For floating plants... wisteria is a great option!!! (I am currently using blyxa as my floaters, just because they are a high light stem plant and werent getting enough planted...and wisteria looks amazing planted!!) Wisteria, if I recall correctly, needs more light if planted than if floated...which I guess makes floating it ideal!
Other plant options, do you have any java fern? Its a beautiful dark green color.
The baby tears would look great in your tank, I want them in mine, but I dont have a high enough light for them to thrive.
There are TONS of stocking options. The biggest issue with focal fish is that there isnt a whole lot of fish that dont need to be in a shoal that can get along with shoals or other fish that fit the tank size. But I know exactly where you are coming from with your wants for that!!!
And your tank looks AWESOME!!!! Great job on the aquascape and decor!! I love that you mixed naturals with theme!!!