I had problems with mine when I first got it with one of the Amiga cores on some monitors but the AGA core always worked for me, I have a BENQ 702A and an old Samsung Syncmaster 914V. i also had issues with some other non Amiga cores, Atari ST and Mac core work fine although I sometimes have to adjust screen positions when changing cores. I bought my MiST a couple of years ago and I am not sure what the newer version differences are.
I have a Raspberry Pi 3 setup with Ambian and while it is impressive for a $35 computer, it doesnt feel like real hardware to me, the MiST does seem almost like a real classic computer to me. I also have the FPGA Arcade board, it does RTG graphics but it is seriously lacking in cores compared to the MiST.