The ARC reactor is a tokamak design though, just (I appreciate the work this word is doing in this sentence) smaller and with much more powerful magnets. They quite explicitly want to not have a different type of reactor.
Problem w/ the ARC reactor is that it is just a design. The real life engineering challenges are still daunting. E.g. for the supra conductors at the Wendelstein 7-X, which provide a much less powerful magnetic field, just assembling and connecting the supra conductor cables for each module was a mind blowingly complex and fickle process that was described at length in this (unfortunately German) super awesome podcast [0].
ARC is not designed to be cheaper or faster to build than ITER. Its purpose is closer to that of DEMO (engineering breakeven). ITER data will be critical for verifying the ARC design.
I thought that one of the very fundamental ideas behind ARC was about trying to get the scale down so that it can be built more cheaply and quickly (not requiring global collaboration).
In the talk here: https://www.youtube.com/watch?v=KkpqA8yG9T4 he talks about ITER being too slow. Certainly the smaller SPARC reactor looks like they want to get things up and running far before ITER is performing fusion experiments, and the possible timescale for ARC is before
While their timescale might be optimistic or wrong, it doesn't sound like they're planning to wait for ITER.
I'm not in the field though so things might not match up with this output or I'm missing something obvious.
[0]: http://alternativlos.org/36/