I don't think there are any big/necessary recent changes in the release that would indicate you need the latest. (Kovid is betaing Version 6, so most updates fix broken feeds)
Calibre Portable is self contained (no MSI) when installed. Common usage is a USB stick, but you can install to a HD (NOT in Program files).

copy your Calibre Config folder contents into the The Calibre Settings folder IN PORTABLE (after the install). You can leave the Library, just know the you will need to switch to it EVERY TIME you run Portable (For true portability, the Library must be in the proper place
on the stick)