1 - yes, absolutely. It uses Smart State to remember the state of all devices and only changes what needs to be changed.

2 - Smart state is designed to handle power toggles like your TV. It knows whether the TV is on or off (more precisely it knows whether IT turned the TV on or off) so when you hit Watch Projector it will either turn the TV off it was on or leave it off. It won't send a power toggle unnecessarily. This is where the Harmony has a huge advantage over most other remotes - if you were using a simple macro you'd have to use 2 - one if the TV was already on and another if the TV was already off. Smart state figures it out dynamically and it doesn't matter what you were doing previously.

3 - there is an OFF button that is essentially an activity with no devices. So when you hit OFF it will turn off everything that was on.

Harmony's have the highest WAF available - my wife even calls it the female remote - just push a button and it does everything for you.

And if something doesn't work right - a command is missed, someone walks in front of the TV at the wrong time, etc. - you just push the HELP button and it will first try to fix it by automatically resending certain IR commands and if that doesn't work it walks you through a series of questions and answers and sends the right IR codes based on that - e.g. is the TV on, is the TV on input1, etc. Can't get any more friendly than that despite what the custom installers will tell you.