Someone in the Forum (Hikashop) said to leave Jommla U.M. to yes. That HikaShop will still add the user info to Community Builder User Manager.
I'm not sure if HikaShop has a CB integration or not. If they do they should check CBs registration settings and use CB API to create a user. If not then they're creating users likely through Joomla API and it will not push to CB. We do join _users, but they will not have a _comprofiler row and will be out of sync (unconfirmed and unapproved).
My question is: What will happen?
You'll have a backdoor registration inviting spammers to slam your site.
You can install our free CB Core Redirect to ensure core Joomla user object can not be accessed (it'll redirect to CB as needed) to avoid this, but I don't know if it'll negatively impact HikaShop.