I had a similar experience, with trying to add mods, but all the issues were how i was installing them, after several install attempts, i realized to do a clean install, clear all saved game data, and them install each mod seperatelly i was able to see what would and not work for my setup. With all that being said, i now run GTAIV with LCPDFR, ELS, SNT, SPOTLIGHT, TOW, Vehicle controll, Traffic control (from here, only traffic mod with taxis fix that has ever worked proplery for me), Braveheart's policing script, v5 graphics tweak, many modded cars, and modded police vehicles. I can play GTAIV with all this and has not crash once.
The lesson I learned was, find out what works with the machine you have, and install the mods one at a time and test them to see if certain ones gives you issues. To many people install all the mods an once and then try to play, only to crash the game and then vent about it. The answers are out there, with some minor research, they can be found. Don't forget, if your having some type of crashing issue, someone else has already probably all ready experienced it and has already done all the hard work to resolve it.
LCPDFR is one of the closest mods of experienceing the role of a police officer out that i have ever come across, add all the other smaller mods that have come out, have put this over the top.
just my 2 cents.