The LN is a 2nd decentralized network that uses the BTC network.
In itself it doesn't change BTC by the very fact that it is a second layer technology.
Limiting the blocksize does of course change BTC. The LN doesn't.
LN would actually be useful for micro-transactions (less than a penny) for pay as you go services. But it cannot be a replacement for the blockchain, like blockstream is pushing for.
Is there even such demand? It will be a lot of hassle for saving only a few pennies for most people.
I can imagine tipping or donations being useful for LN, although better solutions do exist.
Three need for the recipient to create an invoice to initiate a TX precludes it being used for tipping.
