You can use an external wifi drive but you'll have to access it from one of the myriad Android file managers/browsers available. The PB doesn't natively support SMB/CIFS (i.e. "Windows Network Share") connections, so you have to go through the Android runtime (which has the support built-in courtesy of Google).
Other solutions claim to allow native browsing, but they all involve mapping the PB through a Windows PC first and require proprietary software to be installed on the PC that is doing the mapping.
So, if you want to be able to directly access a NAS or similar device, you'll need to get familiar with Android file manager apps running under the PB.
Note that Ghost Commander will do the trick and is available in AppWorld. And if you know how to sideload, ES File Explorer is also an option (and my preferred file browser).
Hope that helps!