Well, it all comes down to tastes and preferences, but Linux Mint is made to be a very easy transition for (ex-)Windows users. It works out of the box, looks intuitive and has great support on their forums. Give it a try and if you feel like you want to try out other distros later, it all gets easier once you are familiar with Linux overall.

And yes, what you mean is dual booting and Mint asks you on install if you want to choose that option and sets everything up for you.

Ubuntu or Linux mint are good options. There are other newbie friendly distros out there, but I only tried these 2.

Yes you can dual-boot. When you start your computer, it will show you a menu where you can choose between Linux or Windows.