These are all extremely rough missions.
Planetary Assault missions start with a hot-drop about 50% of the time, and the enemy gets a weight class bonus. Lots of Stand Up missions where the point is simply to kill or be killed, and the ability to fill an objective and "declare victory" is more limited. Lots of enemy defensive installations AND your command type is almost always House Command, which simply eats up your ability to reroll battle conditions (you fight when and where your employer tells you to).
Security Duty is a defensive contract to guard a particular installation, and can involve defending against hot-drops. If the installation is destroyed or captured, you auto-lose the contract. The nice thing is that it commonly defends a factory (which means you get factory repair mods and can sometimes buy the factory product for cheap), but in this specific case, there's noting of significant import on the planet. "Rebels" can pull from civilian RATs or any Successor State RAT, so it's a huge variety of OPFOR.
Guerrilla Warfare means that you have EXTREMELY limited access to acquisition rolls, no access to unit or personnel market at all, and all repairs are considered "in the field". There's *lots* of Random Bonuses for winning it, though.
Diversionary Raids are basically you guys dropping in front of a major force and saying "hey look! We're a distraction!", and letting them chase you around while another unit is either rescued from the planet, or uses your distraction to achieve an objective. You're on the run for the majority of the contract, though it can end early quite often and, again, employers are generous with Random Bonuses and Employer Awards for your service. And in the case of Victoria specifically, the surface is mostly desert and the cities are all underground, which means we're going to likely see the subterranean maps come out (ie, Ishayama Arena maps in a company-sized engagement).