I have installed proxmox in zfs raid mirror 2 x 250GB NVMe => first pool
I have created second zfs pool as raid mirror 2 x 1.6 TB SSD => second pool
I have created third zfs pool as raidz1 4 x 2.4 TB HDD ==== => third pool
You can add new drives to your pools but how to do it and what the limitations are depends on the actual pool setup.
For example adding disks to your first pool is complicated because ZFS is only used on one partition and stuff like the bootloader partition and so on need to be copied manually.
For the second pool you can only add drives in pairs. So you would need to add a additional mirror to get a 4 disk striped mirror.
For the third pool you could add single disks but that will only increase the capacity and not the performance. If you want the full performance and capacity you would have to destroy and recreate that raidz1 pool.
one more question please is when I do reinstall for proxmox on the first pool disks, the new installation will not detect the second pool and third pool.
How to arrange for all pools detection after new installation?