Hi
As Fox says, the zoom filter is good for a light rays effect.
There is a tutorial from Ripple Training that might also give you some ideas.
https://www.youtube.com/watch?v=hOPZiOOD_jo&list=PLj5Nh9NxSxdlJrabzcJlpVtzG6n18D5Cn&index=25
But ..I think you might be describing something else though, like a cartoony style, like the image? Is that right?

There's a generator in your library '2 color ray' that you can adapt for it..using masks to form circular area.
Or, as you said, you can work with replicators and make this sunburst easily. That has more advantages with the various parameters you can use to animate. You have various parameters in the replicator for rotation and scale etc If you want to animate the elements of a replicator independently then you will need to learn how to use the sequence replicator behavior.
https://support.apple.com/en-nz/guide/motion/motn1531eacd/mac
Keep in mind - like you would create an opacity adjustment layer/opacity mask in a vector graphics app, you can use the same steps in Motion to get the opacity running from centre outwards in the sunburst.
About the outline VS direction/fill - we discussed this a while ago on another topic. If you set the outline to under the fill, then the outline will adjust without pushing into the fill area. But if you just want an outline - no fill, then the only method I know of is to make a compound shape - you will use another shape to clip the outline to that the outline appears to only increase outward and away. Here's a project file with both examples. This is how I work when I need the outline to stay clear of the file or inner area - there are probably better ways but I have not discovered that workflow yet.
https://www.dropbox.com/s/xtsg9zey0v0lgjz/Outlines%20Demo.motn?dl=0