Every place weather is different and will struggle with different things.
Once that said... I also have a 20gal tank, to warm the hot side I used to have an UTH and a 100W white and red bulbs (day/night) but they didn't warmed the same way, I didn't wanted to struggle between light and heat so I switched. For lighting I now use a LED strip all around the tank, awesome, it's dimmable, and it has a very wide range of colors. And to heat a ceramic infrared heat emitter, it is still a 100W but it is way more powerful than the light bulbs, had to plug it in with a dimmer and keep it steady below half of the power.
As temps went higher humidity went down, to solve that I covered the lid with aluminum foil and since the ceramic is not the lighting source I didn't had to make an opening, just cut open a little door my lid have, also serves for ventilation.
I also keep the UTH with a dimmer which I also regulate extremely low, it gains only a couple of degrees on the floor no real impact on the tank climate. I don't trust them either but my Kira finds it comfortable.
The only truly expensive item on my setup is the ceramic heating thing. But worth every cent.
Hope this helped, and keep us posted on how things go!
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