I have not seen delays when both the switch (Hue) and lamp are managed by the Hue hub.
Yes that is to be expected, because the logic within the Hue Bridge is fully event-driven, so when the motion sensor signal is received by the Bridge, it immediately triggers the relevant action (turning on a lamp). The problem is that it does not offer this “trigger” to external clients such as a Homey app, so the Homey app must poll instead.
I have seen a 2 seconds max delay when the switch (Xiaomi) is managed by Homey, and the lamp by Hue.
Again that’s a different situation, because Homey is managing the switch and initiating the trigger so no polling required.
I suppose the speed/quality of your WIFI and Zigbee networks have a lot of impact on the delay.
It could do, but I think it should only be noticeable if the network is sufficiently bad to often require multiple retries to send a signal and receive the ack. In this case you would expect the trigger to sometimes be missed altogether, so sometimes it’s slow, sometimes it doesn’t work at all.