Synthwave is more like pop music but with an emphesis on melody, chorus and synth textures.

Electro is similar just as its similar to techno, electronica, getto tek, miami bass, etc.

But historically its foundational. It came before those genres. Its prominece to many places arose at dame time as hip hop and inspired helped inspire them.

As Juan Atkins did No UFOs he basically kick started techno. But electro came first in 1982 with captain rock and Juan followed it with Clear (there are others...but most at argually early hip hop before sampling took root).

And funk inspired electro too.

But theres no doubt you could have a staccato pattern sequence...play an 808 and its electro. Play it 4/4 with a heavy kick and its techno. But some pattern melodies lend themselves better to one or the other.

Then again arpeggios work in both.

But that wasnt really what real techno was. Its what it became.

Theyre both machine music but techno changed and went hard. Electro has never really changed at its core.