It's obviously a bit of a 'spectrum', but I'd say a 'real' hardware startup would be one that develops new hardware, like Tesla, General Fusion, a robotics company, etc - really anything where the innovation is in the hardware, and if software is developed (usually will be) then it sits on top of that novel hardware. Let's call this case 'hardware-heavy'.
In the hardware-lite case, you're basically starting a software company that needs to set up a supply chain for a few parts, built by others, which provides the most cost-effective platform for your software to run on. You might then package that up, brand it, and sell it. This can be relatively capital nonintensive.
In the hardware-heavy case, you'll probably need quite a lot of capital. This will be needed for you to patent your invention(s), prototype your devices repeatedly until you've arrived at something commercially viable, set up a small batch manufacturing process to produce small volumes of prototypes. With hardware, when you ship something anyone can take it apart and reverse engineer it. Every time you replicate your product, it takes time and money - unlike software.
Tons of commenters here will be able to give you excellent advice about the hardware-lite model, because this is HN. I suspect there is less experience of hardware-heavy business models here.
Which fits your vision?