Yes, both, on CPU or GPU. EEVEE is the fastest. For close-ups, Cycles on a graphics card draws every spark perfectly round.

Aatish FX Lite is free on BlendKit: 12 classic shells, the show controls, a night sky, bloom and MP4 rendering. Pro (this product) adds 250+ presets, festivals, text and picture fireworks, ground crackers, real sound, music sync, the Realistic look, smoke, scene lighting, Light FX, the per-firework editor and all render formats.

The add-on is pure Python and Geometry Nodes, with no compiled parts, but it has only been tested on Windows so far.

Yes. The fireworks are saved in your .blend file, so it renders on any machine, even without the add-on installed.

Yes. The sounds are placed in the Video Sequencer and are mixed into MP4 renders.

Yes. The sound recordings are CC0. Six animal pictures (dragon, dolphin, elephant, unicorn, eagle and swan) are based on CC BY 3.0 icons from game-icons.net; if you publish fireworks made from those six, credit game-icons.net.

Keep Light Viewport on (Selected Show → Advanced). The final render always uses full detail.