Can LN clog main chain BTC?
The answer is yes, but not anytime soon.  Also, it's a function of how frequently channels are opened and closed, which can be estimated, but is not "really" predictable.

If you read the LN whitepaper [link], it mentions in the conclusion that "to enable 7 billion people to make two channels per year with unlimited transactions inside the channel, it would require 133 MB blocks"