Can you add a link where Athom says it does?
(I know the marketing is ‘forgetting’ some important con details at some points)
Flows are never slow. It’s either the sensor or the light, or both (or their wireless protocol).
You should add notification- or log cards, like Simple Log, to be able to discover what’s going on.
Simple Log records timestamps with 3 fractional seconds.
- log is written at the same time as the sensor signal: issue is with the light or the wireless signal
- log is written at the same time the light turned on: apparently the sensor reacts sluggish or the wireless signal has issues
Ikea devices use Zigbee, make sure to create a good Zigbee mesh.
Also make sure the Zigbee signal does not interfere with your 2.4GHz wifi signal. Wifi signal from closeby neighbours can interfere as well.
Detailed info here.
I can’t say anything about “the light”, while you forgot to add all useful info.
Request for support, Homey is not a static environment, but not the quickest with supporting new devices:
https://request-a-brand.homey.app/boards/request-a-brand
You should already be using a 5.2V power unit; 2A or up will suffice.
I don’t know what “stronger” means.
Can’t hurt, but old news.
The power could drop a bit with a long cable, but the 5.2V power unit should suffice.
That won’t change a thing for Zigbee devices, or Z-Wave, or bluetooth, or 433MHz, or IR, or Matter.
Personally I’d buy an ethernet dongle right away
Homey is of course not a miracle solution, it’s just a pretty versatile box.
You have to get familiar with it, especially tuning the wireless signals should be done very seriously.
So don’t expect it to run perfectly on day one.
This forum is very helpful, so you should be able to get it running fine.
As I mentioned with “the light”: please provide for device information (product link, brand, model, wireless technology) otherwise it’s like looking in my glass bowl 
