-Is it necessary to use glass break sensors when there will be motion sensors in the same rooms/garage?
In my opinion, yes, it is necessary to use glass breaks in rooms with motion sensors. Door/Window sensors and Glassbreak/Shock sensors are designed for perimeter protection. Motion detectors are designed for interior protection. A properly installed alarm system will cover the entire perimeter and only rely on motion detectors as the last line of defense. When the system is armed at night, or when you're home, the motion detectors won't be active, only the perimeter sensors will be monitored, however, there are exceptions to this rule (night stay mode). Night Stay will allow you to select a specific motion detector(s) to activate at night time when you go to sleep. For example, at night time everyone sleeps on the 2nd floor and you have a motion in the basement you want active at night, night stay mode will allow this motion detector to trip the alarm, however it will ignore the rest of the motions in the house.
There will be one sensor outside on a cover that I'll put over where the Internet connection goes into the house, so if there is tampering with that, I'll at least get a warning before they clip the Internet.
If the sensor is going to be exposed to the elements, make sure it's rated for it. If the sensor is going to be wireless, you're going to have to use the Honeywell 5816OD
It appears cellular monitoring of this system is about $35/mo vs simply safe at $15, so unless I'm wrong about the cost of cellular monitoring, I wouldnt care about the gsm cellular monitoring on the vista system.
The monthly cost of the Vista system is dependent on which alarm company you choose to use and the extra features you select. When I first signed up for AlarmGrid, I selected the $30.00 a month package. This package gave me internet/Cell monitoring with Total Connect 2.0 (remote arms/disarms, email/text notification etc) The $35.00 a month package now includes all of that plus the option to remotely control z wave devices. That package use to be $40.00 a month, but it looks like they combined those two packages into one and made it $35.00 a month. If you call and ask, they might offer you the $30.00 a month plan without z-wave.
Geoarm would monitor the system with IP/GSM for about $23.00 a month, however, I choose AlarmGrid due to the better customer service and other reason.
Expansions for zones on the Vista 20p appear to cost about $80 for wired and $80 for wireless.... can you use both wired and wireless expanders at the same time as long as you don't exceed the 48 zones? Or is it limited to one or the other? If the cost of the Vista 20p is at $150 and the zone expanders put it over $300, wouldn't it be wiser to just get the Vista 128, or will it not work with the envisalink 4 to self monitor?
Yes you can use both hardwired zone expanders and a wireless receiver at the same time. No, it would not be wiser to get the Vista 128, you would still need to buy the zone expanders. Do you plan on the system being monitored by a central station, or are you going to self monitor with the Envisalink?
Are there different zone settings? IE: I want all sensors active when I'm gone, but only want door/window switches active (motion sensors deactivated) when I'm sleeping at night.
Yes, there are many different zone settings, in the manual these are called "Zone Types". You can even create a custom zone type. Google vista 20p installation manual and read up on all the zone types. The basic ones are Entry/exit, perimeter, Interior follower, Interior With Delay etc.