There isn’t a way to filter out transactions from specific accounts (though that’s a great feature request idea. Your sheets will continue to work as they always have, so there really is no need to transition right now. You also don’t need to combine the Net Worth Tracker into the Foundation template if you wanted to keep those separate. You could start in a blank sheet and feed the data for investments into it and then install the Net Worth Tracker using Labs and then just have a separate Foundation template sheet.
Let me know if you have more questions on that.