Office 365 stand-alone or subscription-based installation comes in two versions and you have to opt for either a 32-bit or 64-bit version. Available Office options are the newer version 2019, 2016, 2013 and 2010.
On the newer versions, later than Office 2016, Microsoft says the “64-bit version of Office is automatically installed unless you explicitly select the 32-bit version before beginning the installation process.”
Otherwise, all legacy versions by default install 32-bit unless 64-bit is explicitly selected. So there are still explicit benefits from office 32-bit vs 64-bit.
The only benefit to the 64-bit office is that each individual application would be able to address more than 4GB of ram. Hence Office 64-bit is only needed for enormous files that would require >4GB in-memory processing in addition to page files.
It also requires that you have Windows 64 bit and more than 4 GB RAM installed. It is otherwise not any more powerful or faster than 32 bit Office Pro Plus.
Additionally, older 32-bit add-ins for office are actually incompatible as they can’t be called from a 64-bit application.
The ideal time to use Office 64-bit is in the following scenarios:
You’re working with large data sets
You’re working with extremely large pictures, videos, or animations in PowerPoint
You’re working with files over 2 GB in Project
You’re developing in-house Office solutions like add-ins or document-level customization
You’re working with the Large Number data type in Access
The ideal time to use Office 32-bit is in the following scenarios:
64-bit operating system with ARM-based processor
32-bit operating system with an x86 (32-bit) processor
You have less than 4 GB RAM on your machine
You have 32-bit COM Add-ins with no 64-bit alternative
You use 32-bit controls with no 64-bit alternative
You require Legacy Equation Editor or WLL (Word Add-in libraries) files in Word
You have an old embedded media file in your PowerPoint presentation with no available 64-bit codec.