Depends on the cameras to some degree I suppose.
How about a short straight pole with pole-mount brackets turned in different directions? Or the one you show with other pole-mounts on the arm.
Or nicer and/or if a PTZ involved, maybe a parapet mount like this with others mounted on pole-mounts?
us.dahuasecurity.com
Take a look at the mounts on Dahua, Hikvision, Axis, etc, sites., e.g.:
us.dahuasecurity.com