I know that both carbs and sodium retains water, but is there a difference in the appearance when retaining water from carbs vs retaining from sodium? Because i tend to notice that i become more "puffy and tired-looking" (and feeling tired!) after a sodium meal more than after simply eating rice, oatmeal or something like that, where the sodium content is low.

Sounds like you may have answered your own question. I suppose there is a difference of how water is used when one is over carbed or over salted or both. The body is an interesting thing. Keep experimenting and recording your data to share How one looks is hard to measure because the one that is doing the looking is generally biased. Maybe a third party can help with your experiment.

Salt doesn't make me tired and carbs do.

Same here. Carbs always make me puffy & exhausted, but salt energizes me. That's why we need to see what works for US specifically.