I'm not familiar with Tactrix or OpenECU, so I'll just speak about BMW software and Chinese cables.
I have dealt with what BMW calls an Electronic Control Unit using the BMW software known as Progman (along with Ediabas, Inpa, DIS/GT1, NCS, etc.) which requires a RS232 or USB adapter to the vehicle 20-pin Pacman or
16-pin OBDII port & Windows software to "code" the dozen or so ECUs on the bimmer.The common Chinese L-Line, K-Line D-CAN cables work just fine.