We can look at these one at a time.
Fish Finder: If you are using the built in Fish Finder on the TZT3 then YES, the TZT3 update will update the internal sounder. If external (networked) sounder see here under TZ Touch/2/3 SENSOR UPDATE - HISTORY. See if you model number is listed. If the model is listed then you can use this SW load to update: https://v1.furunosoftware.com/auth.html
RADAR: Same SW link as above.
SCX20: Same link to SW page, scroll down to SCX20. This update requires a windows laptop.
Depending on the model number of the autopilot as to the update method but, they are done independently of the TZT3.