Violent Afib/Mild Afib

My heart rate at onset Afib episode can reach 240+ Rapid Ventricular Response ( RVR ). I can hear the heart beats and feel the vibration in my ears. When an Afib episode ( Attack ) starts it feels like my heart is about to explode. I've heard of people being in Afib and not knowing until an ECG shows the waveform.
Could this be due to different heart rates or Ejection Fraction percentage?
Does anyone else have similar Afib and do the levels of severity differ?
Please let me know your thoughts.