** corrected the typo with class, abstract will not be associated with a table.
With 'allow locking: enabled'
Since your class is concrete class, having associated to a table and to modify/update a record, you need to get the lock of that particular record.
If you successfully manage to get the lock by the OOTB methods, you'll be able to update and save it otherwise it means someone has already has the lock and updating the record.
The lock behaviour is same as normal case locking.
2. With 'allow locking: disabled'
When you want to update the record of a particular class with above option disabled, then before updating the record, you don't have to get the lock of that record. You can just update and save it.
The lock behaviour is same as optimistic case locking.
For the 2nd example, you can check 'Rule-Ruleset-Name' class and try to open the record with open by handle (lock checkbox enabled). You'll get a message in tracer that locking is not enabled for this class.