I have two spatial objects (coordinates in `.shp` files) that I want to draw together in `R`, it is using the same CRS (i.e. to map these using an identical, appropriate, projection)

(The `R` code to define a projection is similar to:
`SpatialPoints(coords, proj4string=CRS('+init=epsg:4326'))`)

First shape file has an associated `.prj` that contains:
`GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]`

Second shape file has an associated `.prj` that contains:
`PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Mercator_Auxiliary_Sphere"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",0.0],PARAMETER["Auxiliary_Sphere_Type",0.0],UNIT["Meter",1.0]]`

I tried to do a search using key terms in this `.prj` such as  https://spatialreference.org/ref/?search=WGS_1984 but don't know which of the several projections to pick.

How can I find the proper argument to `CRS()`?