About high speed sync with A7/r
The A7's and other Sony cameras do have HSS with the appropriate flashes. However, I do not believe that there are any cheap Chinese flashes that work with the Sony's. For the Sony cameras the cheap HSS flashes are generally the older Minolta flashes 3600/5600 HSD, older Sony flashes and some Metz and Sigma flashes also support this. For the older flashes the hot shoe adapter is required, or they must be fired in wireless mode.