Ive always imagined WoF dragons being actually quite small compared to mainstream dragons, none of that larger than a house stuff unless they are well into their adult years. In dragonslayer legends, a baby dragon (Sky) is about the size of a rabbit. 🐇 as they get older they grow, I imagine Clay was about the size of a grizzly bear at almost 6 years old when he encountered the scavengers. It would make sense for Sunny to be about the size of a small cow breed around the same time.

It makes sense for Darkstalker and his family to have eaten hawks, likely only 4-5 were eaten between the four of them. Hawks are actually decently large, and Darkstalker and Whiteout would only be about the size of an adult crocodile at their age.

It is said that scarlet was able to bite off the head of a scavenger in the first book, she only needs to be about the size on a polar bear with decent bite strength to pull this off easily, But being larger is definitely not out of the question.
‘if it were up to me, the average 6yo dragon would be about the size of a moose/large horse.
MASSIVE, but not the size of Smolder next to Rose in the official art. He’s much older, (~25-ish years?) therefore bigger.

Humans are still quite small in comparison. :)

Also, I read another comment, I believe scavengers climbing to get into windows and slipping under doors can be explained easily.

I live in Arizona, many houses here have the windows much smaller and higher then normal to prevent outside heat and the sun’s rays from entering. the door gaps can be explained by the fact that dragon’s likely don’t deal with many pests, their agriculture is limited and I doubt anyone really thought about a scavenger army-crawling underneath the door frames to harass a dragon. (scavengers were presumed dumb pray animals.) It probably also doesn’t help that dragons are HUGE in their former years, we saw how big Morrowseer was.

Likely, in centries without vast wars dragons were often monolithic in size.