Both 12% and 14% are probably too much for a panther, unless the foliage is extremely dense at the top. 6% arcadia is the go-to for your average panther chameleon
T5 HO or T8? If its T8 dont sweat it. If its T5, either raise it a foot over the tank, or as others said, wrap 1 layer of window screen around the bulb, and take it off in a year. Even Todd from LYR recomends the screen technique.