What happens if both sides are forced as inputs on the TXS0108E level shifter?
There will be no burning shorts circuits. The drive strenght of the device is quite low. The device is also mostly for open drain IO where two pins actively grounding the line isn't a problem. The internal weak pullup won't kill anything.
I have used the TXB part for SDIO. The TXB is made for push-pull applications. Again, this device isn't capable of destroying things. I had issues where the A and B supply rail were turning on/off out of sequence and this could occasionally lock up the TXB but not to a dead short.