Guide for IP Phones:

Q.  Recommended model for IP phones along with a link to order from Amazon?

Recommended Phones by 3CX: https://www.3cx.com/sip-phones/

Yealink Recommended Models:
Yealink T53, T53C, T53W, T54W, T57W (can be Router phone)
Yealink T4 Series: T42S, T46S/U, T48S/U and others (can be Router phone)

Yealink T3 Series: T30P, T31P/G, T33P/G
Yealink W60 W70, W80, W90 (DECT phone)

Manual to Configure IP Phone on V20:
https://www.3cx.com/docs/manual/ip-phones/

Recommended IP Phone Model: Yealink WB60

Docs link for more info regarding the setup: https://www.3cx.com/docs/

Follow these steps on your 3CX Portal to view the guide for your IP Phone Setup. 

1. Go to Users  
2. Select IP Phone Option 
3. Click on the Configure Phone option
4. Select the model of your phone from the dropdown in the popup. 
5. Visit the "Configuration Guide" link to follow the setup article for your specific IP Phone model.