This is an interesting run down of your thought process.
The first couple of images against the white looked lie they were playing next to a giant window! The silhouette effect is pretty neat; I like that moodier look. So much trickier with flash as opposed to continuous video - both lighting and capture.
You have to consider more in the moment and use your experience to gauge whether the flash is enough/right direction…
Not used a flash in photography before but maybe I should give it a go for greater appreciation of the art form!