I'm not sure on the maximum number of rows but will find out and get back to you.
You can link each field in the table in question to what we call a select list. This standardizes input into any field in DocuWare, table or otherwise. These select lists can be internal to DW or they can be linked to a live connection via the provided FTP site or, in most cases, with a line of business SQL data source.
Typically our customers create an SQL view of the data they want to present in each list or link into an existing table. This way your ERP system and the data being entered into DW are always the same.
In the newest version of DW you can also link the values presented into a field with the values already present in another field. Maybe a cost center only has a certain group of account codes; the system can use either an existing selection in the metadata of the document in either the main document fields or a field in that particular line item in the table to filter or drill down the information in another linked field.
Hope this helps!
Professional Services Engineer