Run, don't walk away from that pet shop lol. I use flexwatt for all my cages as the only heat source and they are fine. You do need to run them on t-stats though as without one, they can potentially be a fire hazard as most can get really hot and if you use cage stacks with no air gap, that can easily overheat with no t-stat.
No BPs don't need belly heat. They will do fine with an ambient temp of mid to high 80s as long as you have a cool spot in the low 80s they can get to as well.
Heat rocks are the devil and you should run from those too. Like mentioned, since you have a wooden viv, belly heat isn't going to work well for you unless you use a Kane heat mat which are made to go inside the cage but still need a t-stat. You can use a RHP or CHE but I would personally use a RHP over the CHE. Much safer.
Heat bulbs if they mean by light throwing bulb will sap the humidity out of the cage and at night, you will be stuck with no heat as you cant leave the light on 24/7. If they mean CHE as heat bulb, those will work assuming you have a hole in the top of the cage and got screening betweem the bulb and cage as those get like 500F and will instantly kill your snake if it touches that thing. You could use a cage around it inside the cage as I guess a lot EU guys do that but I wouldn't personally. Anything that hot, I wouldn't want inside my cage at all.