Hi,
Changing the quantity can be done with the pagination system.
It's activated by default but you can turn it off in the HikaShop configuration with the setting called "pagination". So if it's turned on, you should be able to do it.
Regarding the display, there is no system to let the customer choose the display mode. You can however configure several menu items via the Joomla menu manager, and configure them with different display modes. You can them add links between them to change the display mode. So it's possible with a bit of tweaking in the view files of HikaShop.