Altheasuite

You can definitely use your existing printed barcodes. While creating products in Althea Suite just enter the barcodes you have already printed. 

Yes, you can create as many retail outlets as you want. 

Yes, you can create as many employees as you want. You can also have a separate login id for them based on the subscription plan taken. 

There is no limit to having products in your catalog. You can add as many products as you want. Your subscription plan might upgrade to higher version after...

Yes, Althea suite is integrated with Quick Books online. 

Yes, you can very well manage inventory from Althea Suite.