Can I setup FYI with only Xero Tax, or do I need Xero Practice Manager?

You can setup FYI with only Xero Tax.

If you do not have Xero Practice Manager, FYI will only sync your Clients. It will not sync Jobs or Time.

Refer to Enabling Xero Tax Integration (Australia Only).

If, at a later date you choose to use Xero Practice Manager, no change will be needed to your FYI instance.