According to the DB product people, you are limited to 500KB per record. There are no limits to number of fields you can have.
But I have 60 KB file in one cell and after few records it shows error 'pay load too large'. It suggests that there is some limit either on account of number of characters or total file size in a row.
If you need further details or clarification, I would recommend contacting the Wix support team, as they know best.
Yes I asked Wix support team.
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