all connected up in parallel with the alarm plug pack, seem to be no adverse effects (alarm is reading normal voltage, doorbell is fully operational)
now just to sort out the other little quirks with this doorbell, like "No platform access" when i hop onto another ssid with my phone, and not recording motion events on NVR...
its been a couple of months so i thought i might update this. the doorbell is going fine and the image is great. night is fine too, as there is a sensor porch light so video is hardly ever in IR mode. notifications also seem to work via hikconnect (although other than my own testing, Ive only had 2 visitors who pressed the doorbell since November!). When the phone is locked, it does feel a bit clumsy having to open the notification AND THEN accept the call. I missed the first visitor because I just opened the notification and started talking, without realising i needed to accept the call first. makes sense though i guess, because you might want to see who is there before talking to them.
got it mounted on a temporary wooden wedge for a better view of the porch area. i will be making a prettier mosaic tiled mount when i have some free time. the wedge is angled at around 12-degs.
it is powered fine in parallel with the alarm power pack, no issues with either device. thanks for the previous advice. Haven't connected an inline dingdong bell yet.
i also have the same recording issue as above where iVMS4200 on my mac says there are no recorded files, but if I log into the hikvision NVR using internet explorer, the motion-triggered recordings are all there. strange--and a bit inconvenient--but workable (not using an SD card with mine).