I only have the Echo and happen to like it, but I've never used the Google lines. Many people seem to like those, too. The latter just got (beta?) compatibility with Hubitat, but neither is very mature--mostly on/off and dimming are supported, as far as I know.
For the lighting, it sounds like you've got it figured out (and to answer a question in a different post: you'd normally use either a smart switch with "normal"/dumb lights, or a normal/"dumb" switch with smart lights; there are advantages and disadvantages to both, but using both a smart switch and a smart switch complicates the problem, and with smart lights the existing switch, smart or not, is best un-used anyway so the lights always have power to them available to respond to software commands, including on or off). I happened to not like the Osram strips because they weren't bright enough for my whole-room application, unlike Hue LightStrips Plus, but for under-cabinet usage they should be fine. They have many official (and unofficial) extension/connection options available, unlike Hue, and they're a bit cheaper.
For the motion sensor, as with many devices, one thing you have to decide is which wireless protocol: ZigBee or Z-Wave. (There are Wi-Fi motion sensors like WeMo, but I don't think they work nearly as well.) Part of your choice may depend on which type of network you wish to build. I'd say most people have a variety of both devices, though some strongly prefer one or the other. I don't, except for motion sensors I strongly prefer ZigBee: they tend to be much faster to respond, some almost instantly, whereas most/all Z-Wave motion sensors I've used have a slight delay. For under-cabinet lights, this may not be a problem, but for whole-room lighting it's an annoyance when that's my main way to get the lights on. (Which protocol you choose can also matter if you have a large house or dozens of devices, where you many want some powered devices to act as repeaters and extend the range from your hub--if you're just starting out, I wouldn't worry too much about that yet.)
Anyway, back to motion sensors: if you want my go-to recommendation, it's the Iris v2 motion sensor, which is ZigBee. It responds instantly to motion, it's compatible with generic drivers included with Hubitat, it's not too expensive, and the battery (a CR2) lasts a while. They are likely discontinuing them in favor of the new Iris "v3" motion sensor, which I've never used but at least one person here has reported to work well. (You'll need to avoid the first-generation Iris products, if you can still find any, which only work with the Iris hub.) I also bought a 2018 SmartThings Motion Sensor, which I've found quite good, and it's a bit cheaper but also a bit larger (but does include a mount, unlike Iris).
If you do prefer Z-Wave, I don't have any fantastic recommendations there. If the GoControl one you're thinking of looks like the Monoprice one I have, I wasn't impressed with response time, but the same goes for even more expensive motion sensors (Aeon Multi and the Dome DMMS1, the latter of which was probably the fastest I tried and has since come down in price and would probably be my choice). Most should work, though again I happen to find most Z-Wave motion sensors too laggy for whole-room motion-based lighting. If (that's not a problem for you and) you find one that looks like it would fit where you want it and the price is right, go for it! (I don't categorially hate Z-Wave; most of my smart outlets are Z-Wave, and I have a variety of odd devices like sirens and remotes that also are Z-Wave. I'm just really picky with motion sensors.)
I just bought a Google Mini since I just want questions answered, but it's been useful for announcements and casting audio too. Sits right next to the Echo near the Kitchen.
