It cleans grout easily (especially the shallow ones). You might have to apply extra pressure in the case of deep grouts. Overall, it should give you satisfactory results.
And if you operate it properly, it will not leave streaks. Here are some tips on how to avoid streaks while using Spinwave.
Hold the trigger to leave an even finish.
Reduce the amount of water you have in it.
Ensure that the cleaning solution is enough.
After your wet run, run the mop dry over the mopped surface.