AOA. Amongst Naqshbandi Shuyukh there has been disagreement on Loud and Silent Dhikr. Would it be alright if I follow the opinion of those who were against loud dhikr (like Shaykh Ahmed Sirhindi) and do only silent dhikr?
It is not a difference between halal and haram, rather of preference. Yes of course you may follow whichever master you wish in this matter, but the best guidance is that from a living murshid and Allah knows best.