The verdict
If your customers write by email and chat, pick Help Scout. It gives every conversation an owner and a history, and a help centre lets customers find answers without writing. If your market already lives in WhatsApp, add it as a channel, and keep the conversations in a tool your team shares.
A small shop with a few chats a day can start on the WhatsApp Business app alone. Once more than one person answers, you will want routing and hand-over. Note that you build on Meta's rules for templates and consent. Keep an email or chat fallback in case those change.