Disclaimer; I have not worked directly with the 32-point I/O modules but I am very familiar with the fundamentals of the 1794 platform.
The physical FLEX bus can support eight modules of any type. Analog, Specialty, 8-point, 16-point, or 32-point, it doesn't matter.
1794 FLEX is a 16-bit I/O architecture, so if you have 32-point modules you will have to logically communicate with them differently than with 16-point ones.
The most important consideration is which network adapter you are going to choose. Only the newest adapters for RIO, DeviceNet, ControlNet, and EtherNet/IP support the 32-point I/O modules, and they do so in slightly different ways.
The EtherNet/IP adapter, for example, allows you to make a logical I/O connection directly to the 32-point module, which is less efficient than a "rack optimized" connection but still works. I think the RIO adapter requires block transfers.
Get the release notes for the network adapter you will be using and they will have information on how 32-bit support is implemented in that adapter.
Here's a 32-bit module compatiblity table, taken from the 1794-IB32 installation manual:
Remote I/O
1794-ASB series E or later
1794-ASB2 series D or later
ControlNet
1794-ACN15 series C, firmware revision 4.1 or later
1794-ACNR15 series C, firmware revision 4.1 or later
Ethernet
1794-AENT series A, firmware revision 2.4 or later
PROFIBUS
1794-APB series A, version 1.1 of the GSD file
ControlLogixTM Family RSLogix5000 programming software, version 11 or later