Can I keep WhatsApp Business on my phone and still have the number in Bitrix24?
Yes, in coexistence: the number stays in the WhatsApp Business app and is also on the Business API; templates and the 24-hour window apply, calls do not.
Yes. Choose Add WABA in Connections and, in Meta's dialog, the option for a number that is already in the WhatsApp Business app; you scan a QR from the app and the number stays on the phone. It is then a Business API number too: templates, Meta's limits on business-initiated conversations and the 24-hour window apply, while the app keeps working as before.
Three things to know: a message typed on the phone does not open the 24-hour window for the API side; WhatsApp calls are not available on a number in coexistence; and the import of the last six months of conversations and of the contacts can be requested once, in the first 24 hours after connecting, after which Meta no longer offers it.