There are two completely different LEE Factory Crimp Dies (LFCD) that work completely differently yet LEE gives them the same name (dumb but good for sales): handgun and rifle. And in the handgun LFCD there are regular crimp for revolvers and taper crimp for semi-auto cartridges that headspace on the rim of the case.
The rifle LFCD set use a collet to squeeze the case neck horizontally onto the bullet. While you need to trim rifle cases so they will fit the chamber correctly, variations in case length within reason do not effect the quality of the crimp. You also minimize the possibility of collapsing the shoulder of the case from over crimping. But if you overdo it then the bullet may get deformed.
The pistol LFCD is nothing more than a die that only crimps for either revolver cartridges or taper crimp for semi-auto cartridges. This pistol version has a carbide ring in the bottom so that it you over crimp and the case bulges, the carbide ring irons the bulge out of the case. It may also help for cases that came out of guns with poor support in the chamber area where the gun's feed ramp is located. But in the latter case it may not get all the bulge out.
Setting up a combo seating and crimp die is not rocket science if the press is a sturdy one (most are??). With the die set up to NOT crimp you iteratively seat the bullet until you get the right overall length (you have to over extend the bullet seating ram of the die and take it slow, not fully operating the press handle (just easy the bullet in to the correct overall length). Then you remove the bullet seating ram altogether. You then take the just bullet seated cartridge and slowly and iteratively lower the die to start getting a crimp. Once you have the correct crimp lock the die down. Put the test case on the press and raise the ram to full up and screw the bullet seating ram down onto the case with the bullet (softly). The test cartridge is used as a gage to set up the bullet seating depth. Lock down the seating ram and make a couple more test cases to be sure the bullet seating depth is correct and the crimp is good. if not you will have to duplicate the process again. There is little that can be done other than small changes to the seating depth.
All this being said about using the combo seating/crimp die, it is better to use a separate crimping die as the combo die is trying to seat the bullet while the crimp is being started. The results are not always perfect.
To be clear I recommend the LFCD for rifles but find no use for me for the handgun LFCD. Your requirements may be different than mine.