I started building a drone (quad) and i was wondering if i will have any problems with the accuracy of the signal i am going to send to the esc's. according to mr booth in Can I use the GPIO for pulse width modulation (PWM)? under "What if I need multiple hardware PWM outputs?" "hard real-time" is required for full precision. i bought a DS3231 RTC which should render the Adafruit 16-Channel 12-bit PWM/Servo Driver he is talking about obsolete. so if the pi takes it's time from the RTC i shouldn't have any problems right?
A Real-Time Clock (RTC) is completely irrelevant to the provision of PWM.
All an RTC does is tell a computer what time it is when it boots. It's useful to time-stamp files and so that any on-screen clock displays current time. It plays no part in the production of PWM.
The answer you link to is outdated as far as the Pi is concerned. It reflects a reality in 2012. Things have progressed since then.