Hello,
1. With the use of simple mode backups and if your databases are not split into multiple file groups, your databases and logs could reside on the same volume and lun. SMSQL requires the system and temp database be located elsewhere. The maximum number of concurrent backup databases is 35. it is possible to put up to 500 db per lun however multiple snapshots would be required to complete consistent backups. I would use that as a maximum again using snapmanager to complete backups.
2. Yes if all database files exist on a single lun the restore process will mount a snapshot and copy back database(s) there is no other way to complete this task using smsql and maintaining the original file structure.
I would recommend the following, group database that belong to the same app together and then group by size. many smaller dbs can go on the same lun. Isolate larger db's if there are SLA's around recovery.
I hope this helps
John