How to determine what Grid and datum is appropriate for you.
Grid Settings:
The two most common grid types in the USA would be either State Plane Coordinates or UTM North Zone. If you are only concerned with measuring the displacements and do not need the raw coordinates in any specific system, choose either one based on your location.
State Plane:
For state plane you can use either SPC 83 or SPC 22. These are simply the year each was defined and surveyed. You will find some states have more than one plane and they are grouped into numbers or letters. So simply search for the SPC and the state plane you are located in.
UTM North Zone:
For the UTM zones, look for the UTM North Zone that covers your area, these are larger swaths than the State Planes so are easier to use if you don't need raw coordinates. UTM Zones are used all around the world as well, so if you are not in NA, look for the UTM Zone for your local region.
Datum settings:
Datum's are a little more straight forward than grids. If you do not have specific requirements and are in North America, Choose NAD83(2011). If you are anywhere else choose WGS84. Again the numbers are the dates of the survey. If you have a specific requirement on your project, search for that datum. See below a visualization of what these datums do/look like.
NAD83(2011) for North America Datum
WGS84 Global Datum
More reading https://gsp.humboldt.edu/olm/Courses/GSP_510/SpatialReferenceIssues/SRS_CRS_Define_Project.html
https://www.esri.com/news/arcuser/0401/datum.html
https://mangomap.com/robertyoung/maps/69585/what-utm-zone-am-i-in-#