Install both. Use the 64-bit for working with large image, opening RAW etc., or for large batch operations. The 32-bit version is my default for most...
If I remember rightly that only collects images from subfolders, it does not generate the folder structure for output, but dumps all of the converted...
I copied your four images to a temporary folder and opened on in fullscreen mode. Browsing with the spacebar is pretty much instant. Load times vary...