For EU261, on how it works and what you can claim check out this official guide

https://europa.eu/youreurope/citizen...r/index_en.htm

Just answer the questions. It is really easy to use and hopefully answers all your questions. The important part is always if the delay was caused by extraordinary circumstances or not.

And it does not matter if you paid for the ticket with miles or how expansive it was. The compensation (for flights More than 3 500 km) is 600€ regardless of the ticket price.