Looking at the EM3 ev website in the drop down menu for wheel type it shows
26 inch Alex DH19 disc
26 inch Alex DH19 cnc
26 inch Alex DM24 disc
26 inch Alex DM24 cnc
26 inch Alex DX32 cnc
Can someone explain what the differences are ?
The DH19 and DM24 are meant to be "e-bike" rims, with the DH19 been a narrow profile and the DM24 a wider profile. The DX32 is more for downhill and BMX hence it is a wider profile again and probably a stronger rim as well.
Not sure what makes the first two "e-bike" rims as they are single-walled 36 hole rims ... not exactly uncommon or special.
Alex rims are probably a reasonable step up from a rim sold by Chinese e-bike sellers but in the non-e-bike world tend to be down the lower end of the rim scale. Pretty common as OEM wheels from what I have seen locally on road bikes in the shops.
That said I have them on my recumbent bikes but then getting smaller sized rims is more difficult. I don't have them and wouldn't have them for example on my touring bike.