question

If the Fronius' have the web module installed you can use ModBus/TCP.
https://www.victronenergy.com/live/ac_coupling:fronius
https://www.victronenergy.com/live/ccgx:modbustcp_faq

If not you can use an ET340 for each(or one for all).
https://www.victronenergy.com/live/energy-meters:et340

First of all you have to configure the Symos:

Change the following settings in the Fronius web interface:

• In the Fronius setup menu, set Data export via Modbus to tcp.
• In the same menu, set Sunspec Model Type to int + SF
• In Settings→DNO Editor, make sure dynamic power reduction is set to No limit (this is the default).
• In Settings→DNO Editor, make sure that in the 'Controlling Priorities' section that 'Controlling via Modbus' is set to be priority 1.

Use the Fronius Zero feed-in active menu item to double check that all above criteria are met. It will show No if the firmware requirement; the Data export; or the Sunspec Model type settings are incorrect.

Do not use a Fronius Smart Meter for limiting export when part of a Victron ESS System. More details about when a Fronius Smart Meter can, and can not be used is explained here.

Then you set the Symo in WLAN-state. After that you start finding the Symo for CCGX. How this works is discribed here:

2.2.2 Adding Fronius to the GX Device

AC-Coupled PV with Fronius

Hope this helps.