The V3 will be good and is nice to have if you are planning on running a bigger turbo. If you're planning on staying stock, afik, a V2 will do just fine. I have the Depo which is basically the same as the V2. Even in hot weather, it keeps temps ~8-10 degrees over ambient.
The radiator is a HUGE upgrade. Made a huge difference on my '15.
I've heard that the hoses don't make a difference as the stock ones are actually sufficient unless they're damaged in any way. From what I understand, the silicon hoses are largely cosmetic.
I don't think you need 2 gals of coolant if you're mixing with water. Depending on where you live, you can go 30/70 to water, which is what I did. I'm in SoCal and don't have to worry about cold weather.
Removal from the bottom is what I did. I did a little write up here:
https://www.fiestastforum.com/threads/thoughts-from-mountune-radiator-install.23121/
There's a couple good youtube videos that show you the basics of how to do it without pulling the front clip. With a couple of friends, it took me less than 2 hours to drop the stock one out of the bottom and get the new one buttoned up. That includes a break for donuts.