the current iteration of Knots has the same set of consensus rules as bitcoin
the only differences are what you allow into the mempool, not what you allow into blocks
but my hope is that a big switch to knots serves as an indicator that the people are ready for a soft fork to fight spam, e.g. a blocksize decrease, or prohibiting op_returns with a datacarrier value, or prohibiting OP_0 OP_IF in a script