I did some testing:
iSpeed and iRaceDash worked fine together and so did iSpeed and SimDash.
SimDash and iRaceDash might sometimes work a while, usually 1-5 minutes but once they worked about 45 minutes, but always at some point SimDash freezes and GI Max, tachometer and SPI-D are stuck in what they were showing at the time. When that happens, I have to reboot to make SimDash work again even alone. I tried to kill the process from taskmanager but it won't open again until reboot.