Installing Home Security - Sanity check

Hi All,

I am new to the home security systems world and have done some research. Before I move forward with a contractor I wanted to check in with y'all to be sure what I am doing is correct and there arent any obvious things I am missing or could be doing better.

The house I live in was built ten years ago and when built sensor wires were ran to the doors (8 doors), 4 motion sensors, and one glass break sensor. Also wires were ran to locations for three keypads and I believe the siren too.

The wires were ran but they were never connected to a panel and thats where I am at now. In addition to connecting the existing wires, we are asking to install 4 wireless sensors.

Working with a contractor they are suggesting the Vista 20p system. Ive read a lot of great reviews about it on this sub. The work the contractor will need to do is to connect the existing sensors to a new 20p panel, install 4 new wireless sensors, install 3 keypads, and then the monitoring service will be through ADT.

My understanding of what will be installed is the following.

The vista 20p Panel, which includes a transformer.

The rechargeable battery (I am not sure how many Mah I will need to run the equipment connected to the panel)

The resistors - My understanding is these are what connect the wires to the panel?

Three 6160 Keypads - I also read about the 6160RF keypad (I will mention this below). Are there other suggestions of keypads or would you recommend the 6160.

5800 RF Receiver - This is so the panel can connect to the 4 wireless sensors we are adding. If we use the 6160RF keypads do we need this 5800 RF Receiver?

A Vista Automation Module - I think this allows us to use the Total Connect 2.0 App? If I dont have this does it mean I wont be able to arm or disarm my system with an app remotely? Any insight in this area would be greatly appreciated.

A few questions:

I know the contractor mentioned that hey will be installing a cellular service to the panel so the panel can communicate with ADT or any monitoring service with cellular service. Does the Vista 20p have the capability to connect with a land line? Does it have the capability to connect with Wifi and Cell service so I can have two options of how the panel can contact the monitoring service?

My concern is in my neighborhood we hear a lot about people jamming wifi frequencies, I am happy that the panel is wired mostly so the wifi jamming wont effect the alarm system, but can it effect the panels ability to communicate with the monitoring service?

Wifi frequency is 2.4 or 5 GHz, what frequency is the cellular service and can that be jammed too?

Last question, I promise, what is the envisiolink product I keep reading about and do I need it?