> I assume that all connections use 3.3V signal levels. Should I ever come across 5V signals, I would probably use a larger Julet M8 for differentiation. OpenWrt writes that some routers already ship with incompatible 1.8V or 2.5V logic. Should the time arrive that I need to work with those, I would probably use this little fella called Micro Q ....

At that point please, please, please just switch to the 4-wire configuration exposing V_IO (aka V_target aka ...). So many problems go away when you have that available. It's nice to have at 3.3V as well, but a lot of OTS 3.3V adapters aren't configured to make use of it.