Matrix Error - "Field Limit is too big for your chosen Column Type"
But is the issue related to the size of the Matrix Field? Or overall the number of fields in the database?


Neither. :)

That error message isn't related to the linked Github issue (although I can see how you'd get them confused).

It's coming from the Craft's Plain Text field type: https://github.com/craftcms/cms/blob/develop/src/fields/PlainText.php#L126-L137

There's a discrepancy between one of the Plain Text field's settings in your Matrix field where the charLimit setting on the field is greater than the database Column Type setting for that field can hold (i.e. for MySQL varchar, text, mediumtext, etc.).