Why alpha is the reason to use a sequence
GIF transparency is a single bit per pixel: fully opaque or fully invisible, nothing between. Any soft edge — antialiased text, a feathered mask, a drop shadow — turns into a hard jagged boundary, usually with a halo of whatever background colour was assumed at encode time.
PNG and WebP store eight bits of alpha. Export a sequence and the edges composite cleanly over any background in whatever tool you take them into. This is the reason to reach for a frame sequence rather than a GIF whenever the animation is going to be layered onto something else.