I only just noticed this option for sorting my feed. I do have a reasonably curated selection of large and small and using “scaled” gives the results I would expect across them all.
This is just conjecture from experience, but I would guess that hot is a weighted sort that shows posts in order of upvotes per unit time. While top is net total of upvotes in a determined time period.
Top is most upvotes in a specified amount of time, Hot is receiving lots of reactions around the time you view the filter. So hot and top may overlap but a post with 1000 upvotes in the last week may show below a post with 400 in hot because that post got 350 upvotes in the last hour whereas the one with 1000 only got 50 in the last hour.
Also note these are just guesses on my behalf, I'm not sure how they actually work I've not looked at the code, these answers just make the most logical sense to me.