@robel You can use one Blago's miner instance with different plots (from different wallet IDs). Just point them all to the same pool. You have to do the reward assignment for each wallet ID.
@robel Of course, there are a lot of people who mine with more than 1 HDD at the same time !
If you are using the AIO client, the system will find your plots automatically when you'll click on "start mining".