You can certainly calculate whatever you want and have plenty of tables and complex formulas. For the most part I’m not sure what the question is asking. Is there anything you can imagine doing in Excel or Google Sheets that you’re not sure you can do with Grist?
When sharing with other people, it might get tricky depending on what you’re doing. If everyone is doing their own invoices, quotes etc. then it’s fine. Each person can add their own record to the table, and so even if everyone is editing the same table at the same time they won’t interfere with each other. Multiple people can even edit different parts of the same record at the same time.
But ultimately a single cell can only have a single value at a time which is the same for everyone. Whatever changes you make are shared in real time with everyone. Which is usually good, unless someone else wants to set different values on the same cells at the same time. For example, if you’re trying to make some budget decisions and you want to experiment with some hypothetical questions like increasing everyone’s salary based on a global parameter to see how that affects overall annual costs, that might clash with someone else’s similar experiments. Even if they aren’t experimenting with salaries, they might be looking into more expensive equipment which still affects the annual cost calculation. If two people need to run similar simulations at the same time, either one of them needs to duplicate the document, or the document may need to be restructured to support it.
Do you imagine needing to do something like the latter scenario?