Hi,
In the front-end, the checkout is the most common way to convert a cart into an order.
About the selection of the variants in the HikaMarket front-end ; it is something we will solve in the next release.
I made a task in the TODO list in high priority in order to fix this issue as soon as possible.
I tried to made a fast fix but I realized that it will require more time and some tests in order to be sure that it will keep the compatibility with the current options and the multi-vendor features.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.