There are a few ways to do this, but I'd probably go this route: https://www.dragapp.com/blog/multiple-gmail-accounts-one-inbox/amp/
Don't forget your Google account includes tech support so don't be shy to leverage that if you need a walkthrough.
It sounds like the only task management software you have is an inbox. Best practices for task management start from the top down. I don't care if it's google tasks or a kanban board, but there has to be something, preferably that is sharable, that can organize tasks from pending->doing->done. Something like this for example.
I HATE GSuite for an Enterprise email, it's to open and an absolute bitch to manage as an admin. Go O365, and don't worry the support doesn't get better when you are bigger. One reason I hate Gsuite for enterprise is the lack of shared mailboxes.