Either 32 or 64-bit versions of Office 365 are recommended and it does not make a difference which version in terms of the "Bits" of MS Office you install. Enviro Data will automatically select the correct version, 32 or 64-bit automatically.

However if you are not using Microsoft (Office) 365, you should ensure that all of your Office programs (Word, Excel, Access, etc.) are of the same version and bits. For example, do not use Office 2013 with Access 2016 and/or mix 32- and 64-bit versions together. 

Note that some features such as the Viewer's internal Map and the secured version of the Viewer (Viewer Only) are not currently supported in 64-bit Access. Other than the map, this means is that if you have a user you do not want to give edit access, they must be running the 32-bit version of the secured Enviro Data Viewer.