0 to 15V PWM Signal method
You are right on both points. First schematic preserves polarity from input to output. But it is often unnecessary. Because most of the time, you can decide on the polarity of the signal from your firmware, you can counter-balance the fact that the polarity is modified if you choose the second schematic. And it uses less components, so I'd go for this option.

R1, R3 and R7 is used to force the transistor off when the PWM output is floating. But once again, it is most of the time unnecessary. From the firmware, make this output a push-pull output, and you can get rid of those resistors. There would be eventually a uncertain zone during the time the MCU powers-up until you configure the output, but this is a very short time, and BJT tansistors don't usually turn on by themselves anyway, unless you are in a very noisy environment. Thoses resistors would be more useful for mosfets, but for BJT, you can avoid them.