HD Upgrade Concern

Hey everyone, I am debating my upgrade and am looking for clarification.

I currently have a 20 bay case with 20x 1TB Seagate hard drives (not NAS friendly). My current Volume has raidz 2-1 with 10 drives and raidz 2-2 with 10 drives.

I want to purchase 10x 3TB WD RED to replace ALL of my 20x 1TB Seagate drives.

Will I be able to do this, allowing me to remove all 20x 1tb drives? if I want all 20x 1tb drives out, do i have to replace with 20x 3tb wd red drives?

Thanks in advance!