You are likely to find that a stand-alone WM requires more manual configuration than a DE. Most DEs have more-or-less unified settings managers, but those settings are really for many disparate components of the environment that a WM won't even try to control. It might be possible to recover some convenience by using a third-party settings manager like the previously mentioned lxappearance (I find the Arch Linux wiki a useful resource in this regard even though I don't run Arch).
Alternatively, you can use xmonad with Xfce (or another DE). That's what I did before completely switching to xmonad and it does make settings management easier.
Also, I find lxappearance an easy and quick way to set GTK themes via GUI rather than having to edit the .gtkrc files for every option.