Regiments I enjoyed played with the most, 75e, 92nd, 91st.
In term of events, the 91st and 92nd. Just like Herishey mentioned it, they both had very high standards in term of participants, maps and overall organisation. 92nd also had a very special touch as we would often switch the regular events to a conquest with insane historical maps, making it even more enjoyable.
That's definitely something which I find missing in the current community.