I like to put my feeders at between five and six feet high. That provides optimal viewing height and is well out or range of cats. Hummers are very territorial. If you have a particularly bad hummer who is preventing the others from feeding, the solution is to put up a second feeder which is sufficiently far away so that the bully cannot guard both feeders at the same time. Because hummers do not live by sugar-water alone.
Real flowers provide nectar and insects that are present around the nectar.
Hummers need both. As an added benefit, many of the plants I recommend for hummers do double duty by attracting butterflies to your garden. And the beauty these plant provide will be appreciated by the two-footed visitors to your garden.