Difference in image scaling between VI, VPSS, VENC

Hello friends! Need your help!

In all hisilicon chips (hi3516c/hi3518c/hi3516a/etc) scaling can be done by vi, vpps and venc itself.
If I want to output several h264/h265 streams that are different in resolution (for example 1920x1080, 1280x720, 640x360), but picture is same.
I can configure one vpss channel (channel 0) and then bind it to three venc channels that will scale my image. Is it ok?

Another way is: make three vpss channels that will scale image and than bind each vpss channel to corresponding venc channel. In this case scaling will be done by vpss.

I don`t understand what is difference in scaling in VI, VPSS and VENC. Could somebody explain me difference?