The limiting factor for ITER was the strength of magnetic fields that could be attained from the superconductors available at the time. The promise for ARC/SPARC at MIT is that the field strengths available have recently doubled, and performance goes something like the 4th power of field strength, so a smaller reactor can reach the conditions that only a larger one could have reached when ITER was designed.
These smaller reactors should be cheaper and faster to build.
The limiting factor for high temperature superconductor magnets will likely be the mechanical strength of the structural steel holding the magnets together, not the limitations of the HTS. This is not a bad thing, just that the HTS are so much better than traditional superconductors at handling high magnetic field strength that you now have to optimize for the steel enclosures.
This is actually refreshingly exciting, coming from the usual "interstellar travel is slow and depressingly hard, space elevators are iffy at best, we probably aren't smart enough to build programmable nanotech" we get from most news updates on future tech.
Are suitcase-sized fusion reactors still on the table, or does this just mean smaller-than-a-football-stadium fusactors are probably possible?
You still need a one meter thick blanket of lithium to capture the neutrons from the D-T reaction (and to generate more Tritium) so you are looking at modular 500MW reactors, although locating multiple reactors on the same site makes sense for fueling and maintenance purposes.
These smaller reactors should be cheaper and faster to build.