And what services will HS2 replace East coast or west coast?
It'll replace the fastest, non-stop services on both lines.
HS2 phase 1/2a (scheduled for completion in 2026) will mean most existing Virgin services from Euston will run as HS2 trains instead. That frees up capacity on the WCML. We don't yet know
exactly what will be timetabled to fill that capacity, but we can reasonably expect to see those services replaced with more commuter trains, and also trains between London and the NorthWest that stop at more places - thereby giving more links from Watford/Milton Keynes/Rugby etc. to Liverpool/Manchester/Preston/etc. (Which will presumably be what the Pendolinos will be used for).
HS2 phase 2 (hopefully complete 2033) will do exactly the same thing for the ECML (and also to a lesser extent the MML). So for example, London-Leeds and London-Newcastle-Edinburgh will run via HS2, speeding up those journeys. And the spare capacity that is created on the ECML will most likely get used to provide more long-distance stopping services. So the Azumas will continue to run, but they'll stop at more places, and essentially be providing better links between Stevenage/Peterborough/etc. and the NorthEast. Possibly there'll also be more commuter services to Kings Cross. I also wouldn't be surprised if the opportunity is taken to run services like Grimsby-Lincoln-London, which I believe are not currently possible because of no capacity on the ECML.