A friend has given me edit access to a Google Sheet he owns. I want to write to it via web server code hosted elsewhere---at Wix, actually, where I've built a page that wants to update the spreadsheet from time to time, perhaps a dozen updates per day.
I have found several technologies that might solve the problem. Google Apps Script is one, the Sheets API another. The latter of these is (as far as I can tell) really three distinct options depending on authentication scheme: API key, service account, or OAuth2.
The question is this: Given my specific situation, which of these four approaches (or others I haven't found) is feasible and most appropriate? I'm not asking for opinions; I just don't want to go down one path only to learn later that it's an unworkable dead end (as preliminary research suggests that API key might be) or absurd overkill (as preliminary research suggests that OAuth2 with a Google-approved app might be). Note in particular that I have edit access to the spreadsheet in question and can give that access to others if necessary. If the choice depends on factors I haven't mentioned, what are those factors?