Cool track! I'm always in the mood for some synthwave.
Sounds like the high end on the vocals has a constant EQ filter, I'd recommend a de-esser (or two?) and a multiband compressor to only filter the high end/ess's when it crosses the threshold. Vocals are also missing some low mids to make them sound full. If they were cut with EQ then I think give em back some body, and/or use a plugin like Waves RBass or MV2 to add some low-mid harmonics.
Harmonies work great note-wise, but it sounds like a few lines could be aligned better with the main melody. Gotta keep it tight! Also be sure to do the same de-essing to those tracks, but even more dramatic to where when solo'd they sound lispy.
Hope this helps!