1) It is an option, depending on your needs. It is easier to sort out usage per customer if they have their own logs. It does not help performance. Avoid making multiple VHosts because it complicates tuning and separating by application is all that is usually necessary for this kind of service.
2) You can use the
PushPublish features to push an RTMP stream to the CDN, which they can distribute as RTMP and other protocols depending on their offering. Or you can set up Wowza as an
HTTP caching origin, in which case the CDN pulls HTTP chunks that Wowza produces that are then distributed in their network for playback by HTTP clients. RTMP playback clients are not supported when using HTTP origin.
3) In live streaming with Wowza, you must pull MediaCaster streams, such as IP cameras and mpeg-ts encoders which publish to a rtsp or udp endpoint and are not aware of Wowza. Live RTMP encoders push streams to Wowza, they publish directly to a Wowza ip-address/app-name. So there is not a choice, you have to use what is appropriate.