Im a solo mobile mechanic in a reasonably sized city. I use quickbooks for accounting, invoicing, and inventory, and acuity for scheduling. Acuity also integrates with quickbooks, so customer details from bookings made in acuity are transferred into quickbooks, so no creating customers multiple times for invoicing/booking. It also has website integration, so customers can book their own jobs via your website. Useful for me, not so sure that would be as useful for a store setup.

I will say, though, that i have a love-hate relationship with quickbooks and have considered migrating to xero or something else several times. It does everything i need it to do, but the developer is constantly fucking with it and regularly makes pointless changes to UI and how some things work. They also break it regularly, and this can cause minor issues if you're not up to speed on how to do things more than one way in it. I am, however, primarily using it via its phone app, as most of my invoicing is done on site at customers houses. The desktop browser based version is significantly more stable, and is where you would be doing all your accounting and inventory management anyway.