Hi,
First, there is a migration tool from VirtueMart in HikaShop:
www.hikashop.com/en/support/documentatio...port.html#virtuemart
1. You can create products automatically from the images in a folder with the import:
www.hikashop.com/fr/support/documentatio...hikashop-import.html
2. You can restrict payment methods to zones and they will only be available based on the address entered by the user, so yes. There is no "pay in advance" payment method but you can use the bank transfer plugin and rename it and change its translations for that easily.
3. There is not direct option for that, but it should be possible to achieve it indirectly. You could have two shipping methods. One for products with a weight, and one for products without. Then, set the payment plugins to be displayed or not based on the shipping methods selected. That way, based on the products in the cart it would display one shipping method or the other (you can easily hide it with css if you don't want to display it) based on the products in the cart, which will in turn display or not your payment method.