Is the air assist worth it on the LX2 for acrylic signage?

Yes, but with a nuance that matters for acrylic specifically.

Air assist does two things: clears smoke from the beam path (more power reaching the material) and blows flame off the surface (fewer scorch marks). For plywood you want it strong. For cast acrylic you want it gentle — a hard blast cools the cut edge and gives you a frosty, slightly cloudy finish instead of that flame-polished clarity. Low flow, just enough to keep flame off.

So: fit it, but put a valve in the line so you can dial it down for acrylic. Full blast for ply and MDF, a whisper for acrylic.

The other half of polished acrylic edges is cutting a touch slower at lower power rather than fast at high power. One slow clean pass beats three fast ones.