I have recently stared using a CRM with a quoting / payment / document portal called Dubsado. This is proving to be very useful. It allows me to sync with G Suite and keep all my client emails under their account. I can create workflows and canned email responses, setup questionnaires and allow clients to pay online using a payment schedule. The client facing end looks very professional and already I have had some clients wanting to use the same system. You can check out Dubsado here
If you are interested and need help setting up ask me for a quote.