In fakt of errorfree transmitting and wider range of ERRORFREE usable Baurates i want to know, if it makes sense to use ...
I think it makes perfect sense to use a crystal that will give you an exact baudrate match - if that is your main priority. Since all mcu timing is derived from the single crystal however, the choice is typically a tradeoff between conflicting requirements, and then the sub-system with the highest tolerance (e.g. USART) is the preferred candidate to compromise.
Examples of conflicting requirements may be:
- Frequency measurement, tone or pulse generation, PWM base frequency
- Software timing loops (one-wire, software serial, micros delay)
- Real-time clock (millis)
- Cost and availability of desired crystal/resonator