Raid-Z and Mirrors will be decided from the size of the smallest disk.
1 + 2 mirror would be 1 in raw space
3 + 3 + 8 Raid-Z would be the same as a 3 + 3 + 3 Raid-Z.
Another issue is all members of a VDEV would need to be replaced with larger drives to get more capacity and expand the VDEV
Try searching the forum for that model and see what others have said or search Ugreen.
Resources may have some sample builds also with features you desire
Resources List including Detailed Hardware and System Build Notes (plus new user advice / help)