For the max light level, look at bulb specs for higher lumens or wattage equivalent to an incandescent, which is often how they advertise “brightness,” in the US at least.
They are, although as @rlithgow1 pointed out, it’s a local integration with Hubitat so that overcomes one of the major limitations for most WiFi bulbs on the market.
If you have generally acceptable WiFi coverage at home, and they’re available in the UK, might be something to consider.
I use Philips Hue bulbs for all of my table and floor lamps. Some of them are the higher Lumen versions. Just be aware that the super high lumen rated bulbs from Hue may be a physically larger form-factor that may not fit properly in your light fixtures.
They have been 100% reliable, although I do use a Philips Hue bridge. I have never tried direct connecting them to Hubitat's Zigbee radio, and thus I cannot say whether or not they might cause issues with your existing Zigbee mesh.
I would suggest Gledopto Pro bulbs: brighter than Hue, dimmable , inexpensive, reliable and perform very well with HE. I don't know if they are available in UK, but you will find it at Ali Express. Although Chinese, Gledopto has a very good after sales service.
I have 15 in my house, connected to HE through a Hue hub.