Those examples are vectors from Freepik.com. I'd recommend downloading them, so you can see how they are set up. The idea when creating a glow with a vector object is that it's going to have a raster effect applied to it (Effect > Stylize > Outer Glow) that produces a glow when it's over a dark background because of the blend mode used in the effect.
I don't think they used outer glow since that wouldn't be 100% vector, which would not comply with the rules of most stock companies.
Also outer glow would dissolve equally around the object, but the glows here are sharper around the edges.
I'd rather assume gradient meshes. Maybe blends. Or a combination of those.
The glow effect which is a raster effect and uses a blend mode is a simplified, general idea of how to add a glow. True, it doesn't have to be a raster effect. If you download the image and take a look at it, various parts use gradients and have the blend mode Color Dodge applied to create the glow.
I've downloaded the vector from Freepik to take a look but for some reason, the background layer is not showing up?
The paths for the vector are visible though. Does anyone know a good tutorial on working with these types of gradients and layer blends? I'm unfortunately not as familiar with Illustrator.
First of all I would zoom out and check if the artwork is somewhere else.
Then try and select the CPU Preview in the View menu. And maybe turn off the top layer.
Try this tutorial
To see the background, unlock the layer first, then on the right side of the BACKGROUND layer there is a circle, click on it, then press Ctrl+-(minus button from keyboard), that will show the background.
works for me...
These are not a once click effect, it is used gradients, effect overlays, and there are many objects used to create this one effect.