I do provide UVB to my snakes, and am not here to argue at all, just to provide some info regarding the OP's original questions!

I wouldn't set up a halogen bulb in addition to an RHP. That's overkill. Go with one or the other as a heat source.

If you are still interested in providing UVB I'd suggest putting this on your 'someday' list, and take some more time to learn about it, as there's a lot to take in, and info about lighting can become pretty arcane pretty quickly. In the meantime you can think of UVB as a supplement rather than as a requirement - unlike some reptiles, snakes don't seem to directly require UVB for D3 synthesis. Your snake will be OK without it, but the research is pretty clear that UVB is beneficial even to crepuscular reptiles like Ball Pythons.

Should you elect to provide UVB, you need to plan for the fact that it isn't cheap. It also needs to be done correctly - the Arcadia Shadedweller bulb is indeed a good choice - because just setting up UVB without correct planning for bulb/reflector placement and clutter/hide placement can be dangerous to your snake. I prefer using a solarimeter to double check UVB levels, and that is another expense.

I almost never recommend Facebook groups, but I do recommend the Reptile Lighting group because most of the admins are veterinarians and/or researchers with decades of experience in reptile heat and lighting work, and the group doesn't permit rudeness or claims that aren't science-based. It can be some pretty heavy reading, though, but the information is well worth it. John Courteney-Smith, who directs reptile/bird science at Arcadia is also always courteous and a great source of information. I could have sworn he used to post here occasionally but I may be misremembering.

So long story short - I do advocate for UVB availability as an option for captive reptiles, I do provide UVB, and I do recommend that anyone interested take their time, do their homework, and consider whether it's an expense they can take on.