KC is a wonderful program to start with.
It is simple, and for the keyboard stuff it is very good.

However the PiP speed and Mouse Broadcasting are not strengths.
And they are for IS Boxer.

I'd recommend doing a trial of IS Boxer, which you can apply for on Lax's site.
That gets you 7 days to use the software and decide if you like it.
The link for a trial is included very early into my guide, which is in my signature.

The basic set up will be done by the wizard, and you'll be up and running in a few minutes.
This will get you the option to switch (almost instantly) from one toon to another.
The slaves can auto follow the new master on a switch, or have no follow option occur automatically.
You can press the follow hotkey manually as well.
By default FTL will have every toon auto assist the main, and do whatever spell is on the same hotkey as the main (press 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, -, =), without the need for any warcraft macro at all.

There are a lot of configuration options to personalize your interface.
If for example, you want it to run similarly to how you have KC currently configured.
Or maybe you'll want to start from scratch.

IS Boxer has phenomenal configuration power, via the mapped keys feature.
Hotkeys which can target the current window, all the other windows except the main, any combination of toons (via action target group) etc.
There are numerous videos on www.isboxer.com, and a lot of users in the IRC for support too (the IRC opens in your browser, and is linked from the isboxer.com main page.

If you decide the software is for you.
Definitely use a referral link when you sign up.
It gets the person who referred you 30-45 days of extra subscription time, depending on if you go for 3 months or a year subscription.
Subscriptions are $10/3 months or $36/year, and you get 15/30 extra days for mentioning a referral.