I have installed coilover sets on two different cars, one on my old 987CS and earlier this year on my 981CS as well, and (personally) prefer Not to mess with the ball joints as there is a chance to damage the rubber booths when removing them from the hub.
Therefore, I prefer removing the bolt that attaches the control (coffin) arm) to the subframe, on the rear axle you also have to disconnect (only one) the half shaft from the tranny or remove the big nut from the half shaft that would allow you to slide the halfshaft from the hub and out of the way.
PS: By disconnecting the control arm from the subframe, it allows to lower the entire hub enough to let you remove the entire strut assembly from the hub.
Out of curiosity, which brand of coilovers are you planning to install?
Please note that in the two cars (987 & 981) even by adjusting the coilovers at their maximum height, the car was still lowered a bit more than one inch, and this required adjustable links (Tarett or Renlinne) to allow you to dial out the extreme toe-in that would result after lowering the car.
Thanks on the 987 we have the KW V3 and we've been happy with them. Still trying to debate the merits of just sticking some H&R springs vs full coil overs. The 981 has PASM so it's a bit harder to find full coilovers for it. But thanks for the advice! much appreciated.