Can twisted pair replaced by two wires which are closely placed?
Old fashioned telephone wires went tens if not hundreds of feet without twisting: -



Picture from here.

Usually, at each pole, a particular single wire pair was positionally reversed to avoid a build up of cross-talk between all the simultaneously utilized phone lines but, in-between poles they were all parallel. So, if your bandwidth is low and your distance is moderate, and your signal-to-noise ratio expectations are low to medium and you have little chance of interference from high frequency magnetic fields then try out non-twisted pair cable.