A: Generally yes you can build anything you want with Apps Script and deploy it as an Addon. But that's only if it interacts with sheets directly. There are some things that people put into Addons that are calling an outside, or 3rd party server. Those things you can't replicate on apps script only. You would need the external server. I don't know enough about Logic Sheets to say you can replicate 100% of it. But sure you can build any google sheets add-ons you want.