There are many variables here. As a general rule, yes, it should work just fine. There are some exceptions:
You must be using a computer. Tablets and Phones are not content creation devices and they may or may not work with the editor as intended due to the under-powered, locked-down nature of such devices. It may work just fine. I can paste formatted stuff in on both my phone and my tablet.
It also depends on what you are using for word processing AND how you have something like Word configured. If you end up with crazy double spacing, you can clear that up on the Word side by doing a find and replace... find ^p^p and replace with ^p.
Even if it looks crazy after a paste into the editor, it might show up fine in the chapter due to our display filtering.
Yes... but you should not be changing fonts and font sizes. It's very likely the system will strip it out so that the chapter formatting tools work properly.
There are some exceptions:
You must be using a computer. Tablets and Phones are not content creation devices and they may or may not work with the editor as intended due to the under-powered, locked-down nature of such devices. It may work just fine. I can paste formatted stuff in on both my phone and my tablet.