Going to different countries in Europe & UK as a Canadian - airport logistics

Hi I’m a first time traveller going to the EU & UK. I’m travelling from Canada & have seen so many different things about travel changes & had questions from any Canadians who have recently (in the last 6 months or less - preferably recent) travelled to different counties in the EU & UK

1. Do I need an ETA?

2. Do I need an ETIAS?

3. With these new systems how early should I arrive at the airport for flights?

4. Is there any other pre-screening sort of thing I need?

I am flying from Barcelona to nice to Amsterdam to London, staying a couple days in each destination.

Open to any other suggestions or tips! TIA