With our Multi-Inventory add-on, you could create as many inventories per product as you need. So you can create one for every e-commerce channel you have. However, we don't integrate with external e-commerce systems at this time. So, for example, if you need to sync your eBay stocks with WooCommerce, you would need a 3rd party plugin and, probably, custom coding to integrate it with Multi-Inventory.
ATUM also has its own POS system but, for now, it's only part of the ATUM mobile App (still in beta) and this App has a barcode scanner, etc
just so you know, there are around 20 thousand products, with variations and they are all currently sat in CSV files ready for uploading from another older website that used Joomla
You could import all your products with our ATUM Export PRO add-on too.