Checking if any word starts with a prefix is simpler. Just verify the path exists:
def startsWith(prefix):
node = root
for char in prefix:
if char not in node.children:
return false
node = node.children[char]
return true
No need to check isEndOfWord. If the path exists, some word has this prefix (possibly the prefix itself, possibly a longer word).
To get all words with a given prefix:
Go to the prefix's node
DFS from there, collecting all paths that end at isEndOfWord = true
That's why tries power autocomplete. Finding all completions of a prefix is a single subtree traversal.