The device needing more power won’t get it, simple. Depending on what device it is, it will automatically throttle down so it needs less power, but obviously it will also deliver less performance while so throttled. And if the power is missing during a very sensitive part of a process so there’s no time to throttle down, your PC could blue screen or restart.
It’s very unlikely to suffer any long-term damage from this.
Almost all of these the game literally tells you about right there in the GUI… When you are building, you get an info bar telling you what button combinations do what. This is smart enough to even depend on what exactly you are building, so it will not tell you about R for build modes when you are building things that don’t have build modes.
Another small thing not everyone knows about: when building normal hyper tubes or pipelines, you can rotate the end point vertically as well. While placing it ( hold left mouse button), you can drag the cursor up/down for elevation, but you can also use the scroll wheel to tilt the connector. This allows for more aesthetic long gradients, without having “steps” on the connectors.