From my experience stages smaller blast zones in general have help secure earlier kills making it better for Corrin. Horizontal kills with f/d-smash, neutral-b (bite), bair, and pin while kills off the top with upsmash, up-air, side-b kick, and up-b.
I agree Lylat is probably one of the better stages because of the platform coverage like you said. The fact that the sides of the stage being slightly slanted also allows Corrin's kill moves cover more. Kills off the top are pretty nice due to the lower ceiling. Reading air-dodges with up-air or up-b on this stage is amazing.
Yoshi's Island I don't like too much because of how the floor geometry at times prevents moves like f-smash or tipper pin (At times the slants can be taken advantage of, I find it far too unreliable). The floor also makes up-tilt and up-smash whiff sometimes if you're positioned on one of the downward areas. I may grow to like the stage but those are my main complaints.The earlier vertical kills on the platform are nice to have as well as a wall to potentially mix up recovery.
I like to play on Kalos a lot, the stage feels perfect for Corrin. Although the side blast zones are larger, the side platforms stick out farther and can be fully covered. Covering landings or any sort of tech on them with bair or neutral-b is very reliable and net the majority of my kills. Recovery on Kalos is also very good since you now have a platform to mix up recovery with (either land or fast-fall through and grab ledge) along with a vertical wall. Another cool thing with the stage is that if you side-b kick off the platform towards center stage you have enough frames to buffer a falling nair or up-air. The best part about this is that you can combo off it into a kill/edgeguard in certain instances they're sent flying onto the other platform. It also puts you in prime position to ledge trap the other ledge of the stage. I've caught a bunch of people (mainly zoners) off guard with this and have netted a good amount of kills.
Town and City is kind of cool since you can shark with up-air a bunch and force them on the side platforms. Once they go away I think the stages is ok at best.
The Pokemon Stadiums are not too special other than the low ceiling.
I hope to see more people pick up Corrin. I've seen people complain about not being to side-b spam anymore but I think that play-style holds her back. Thanks for bringing the stage topic up, good too see what people think and see in stage potential.
