cutting the starter wire

cutting the start wire for starter kill, antigrind or both is nice to have for many reason.

as mentioned above, you dont haev to worryy about grinding the starter if you already have it started already.

and yes solder everything

Had many experiences where people throw thier keys around and break there remote in the process, then cant stop the alarm (or start the car).

In occurances where i do use the start interupt, electrically i havent had a problem.

If you don't solder the wires I wouldn't recomend cutting the wire.  Crimping the heavy gauge wiring or even worse using T-Taps or other methods have a high likely hood of failure over the course of the vehicle.

I've only encountered one issue when soldering the starter wire - the original installer chose a terrible place to cut the wire and then did a terrible job soldering the wire back together.  Luckily, it was the key side so the remote start still worked, otherwise the customer wouldn't have been able to start the car!

I wouldn't use a 25 watt iron to do a starter wire, but I bet it could be done.  When working with any thicker wires in the car I use a Craftsman soldering gun.

The place you cut it doesn't really matter as long as you can access the cut and it's not so close to a harness that you can't splice both sides back together. 

The guy in the car I had to fix cut the starter wire rigth were it comes down from the column.  I had to drop the bottom of the column to get to the wire - he didn't drop the bottom of the column and the results were the connection only lasted 2 weeks.