Basicly never.... I often take my pc to lan partys with my car, never secured the aio or done anything tho prevent my pc from sliding around. I have this Arcitc aio since 3-4 years and it always worked fine.
Installing an aio is easy, sometimes even simpler than an air cooler but they are both easy to install. The only thing you have to watch out for is if your case supports a 360mm.
There are no big differences between most of the coolers. Just take a cheap one form amazon which has the features you want and maybe silent fans.