Hi,
You have the HikaShop option which auto select the payment method in the checkout.
After that, if you don't want to use the bootstrap design, you can deactivate the option (but it will affect the entire site) or you can override the "checkout | payment" view in order to have you own design.
The payment select is not really using buttons, it is using radio with a "btn" class style.
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.