lowering the control arm will allow the car to have more negative camber during turning so the tires stay straighter instead of trying to lean out at the top. the 1" drop helps tremendously with that but the 1.5" or 1.75" drop works even better. is the lower drop worth it on the street? that's debatable but on the track it is definitely worth it.
you could do just the 1" drop for now and later on change to the 1.75" drop but the problem with doing that is you are adding more holes to the shock tower, creating more potential failure points. however you could do the the 1" drop now and later add the TCP control with the offset shafts or do the TCP
control arms with the offset shafts now and later on drop them more, which would probably be the best way to accomplish that, since doing a 1" drop now and adding the TCP offset shafts later would give you a 2" control arm drop which is really too much.
by using the TCP arms with the offset shafts now for an effective 1" drop would allow you to drill new mounting holes 3/4" lower later on giving you the 1.75" drop you're ultimately looking for without being too low or having a mess of extra holes in the shock towers.
by only lowering the mounting points by 3/4" you aren't going to hurt anything, though i would recommend weldiing up the original holes, and by using the offset TCP shafts you won't have any worries about ball joint bind either, plus by only drilling 3/4" down and 1/8" back you have no worries about geting outside of the inner tower reinforcement and weakening the mounting points.
my advice is to use the offset shafts and only drill 3/4" down and 1/8" back. using coilovers or roller perches is up to you but i've been using the roller perches on my car for a while now and i really like them, that said when i get ready to the
suspension work on my cougar i'm probably going to get John at Opentracker to build me a custom coilover conversion using his roller upper and
lower control arms and possibly (probably?) TCP strut rods.