I'm going to buy a Surface Pro 7 and I have two questions:
1. Can I use the type cover unplugged from the Surface?
2. Can I connect the Surface without type cover to a monitor using the type cover as external keyboard and trackpad?
The type cover is not a wireless device. It stands alone, and has no function unless physically connected to the Surface.
However, you can use third party wireless keyboards and trackpads as you proposed. The Surface keyboard does not need to be connected in order for you to use a wireless keyboard, trackpad, mouse, or the like.