[lunatic]

How can I resize mounted partitions ?

You can't. With old Solaris, I think you could also only increase size with "growufs".
Solaris had no proper LVM, but historically used "disksuite". It wasn't bad, just less capable. IIRC the Veritas stuff could be bought as well to add a full LVM, but I have never seen that used by anyone.

Also, when adding a new disk, I need to label it, format and partition, how can I do this ?
I use solaris 2.6

with "format".
After that you can "newfs".

found for a new disk. Need to boot -r

How about something like "drvconfig", "devlinks", "disks"?
Some later Solaris release also added "devfsadm".