Sprite renderer + a Constraint if you need aim/look at/face camera (Unity - Manual: Constraints)
all glows can be dynamically packed to an atlas so they all use the same mat, the sprite renderer also has a tight cutout mesh creation system so it attempts to save overdraw, or use sprite mode Multi and make it manually in unity
Unity - Manual: Sprite (2D and UI) Import Settings reference
also the Line Renderer (Unity - Manual: Line Renderer component) adds some options +its own 2D aim-at-view
using the MeshRendererquad will need dynamic batching if you plan on aim-at-camera. i would avoid using mesh filter +mesh renderer
there is also Glow/lens flare
Lens Flare component is handled like a Sprite, it has this ‘fade-offf’ feature though if something obscures it, which can be useful
post-processing attempts or off screen buffer at 1/10 res etc, they can work but this is a TechArt/shader Engineer task to setup for mobile wisely
i also recommend for glowing/flares to avoid compression,
i use a lot of single channel B&W images (Alpha8 format) or just small 32bit images, keeping res <500, the bilinear filtering + uncompressed images can be fullscreen and look great… FAR better than some 1024 with PVRTC4bpp