basking bulb- depends. I used up to 75 watt incandescents in 10 1/2" reflectors resting directly on the mesh and they were fine. Only the cool edge of the reflector touched the mesh- not the bulb. If you go too high wattage such a setup will be too hot for the mesh. But shouldn't be necessary for a chameleon anyway.
UVB tube- yes amount will be reduced. But should still be sufficient- especially if you are using a 10 or 12.0.
I used a large number of these cages for many years and the UV was never a problem, although certainly less will penetrate the mesh.
A word of caution- a flourescent light ballast I had malfunctioned and ignighted a bank of these cages on fire with catastrophic results. Be careful- the mesh is flammable.