More California Schoolchildren Are Reportedly Stuck In Afghanistan

I got confused with stricter and more strict, strictest and most strict. What is the rule about this or both are correct? Let me make a sentence with stricter dan is stricter than ryan about

What part of speech is 'more'and which word it is modifying? What's more is an expression that's used when you want to emphasize that the next action or fact is more or as important as the one mentioned. War doesn't bring peace; What's more, it brings.