Ive only ever had one copyright strike, that was for a flip I did of "Eleanor Rigby" by the Beatles.
I basically instrumentalised the original by using a mix of the original, the midi and some composition, I did too good a job instrumentalising it. Didnt sound far from the original musically. Since the mid naughties sampling became very expensive in some cases and drove me to become better at composition, I generally compose everything these days and sample for fun to get involved in the sampleflips, and Ill has always favoured sampled beats so if I intend to compete, thats probably the best way to go here.