I would reccomend a snake in the 200g range or larger. Babies can be harder if they decide to go off feed. Larger ball pythons can miss meals for months without harm.
Heat tape is usually very reliable, I'd have to defer to others in brand and sourcing. The most important part is to have a THERMOSTAT to control the heat.
Depending on feed and the individual snake, most will mature in 2-3 years. But they continue to grow for several more years. Many ball pythons will reach the typical size and then level out somewhat unless fed very heavily. They still grow but it's not as dramatic.
A 10g tank should be okay for a while as long as you don't power feed(feed large prey too often). Tubs are better than tanks for holding humidity though, although they don't "look" as nice.
The humidity will lower dramatically in the cage with the heat sources, depending on what type of heat source and what kind of cage. If it's a tank, you probably will not have high enough humidity without covering a lot of the top and such. If the humidity is an issue, you just increase the ventilation and it will dry out the air inside more. In tubs, you just drill more holes. Living in Florida, my humidity stays very high but in the cages, it's always much lower.
You should probably be okay with the adult size. It of course depends on what size your python turns out to be.
Good luck and know that you're doing it right by researching first and getting the snake after.
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