The PDA explains what the enemy difficulty setting does in-game or online here: https://empyrionbuddy.com/pda/difficulty-scaling-eden_pda_iWiqeGs/re2/english

Don't forget you can use the drone to retrieve your backpack, or change what you drop on death in the difficulty settings.

As far as NPCs spawning behind you, that shouldn't happen unless it's part of the POIs design such as a trap. Otherwise the spawners have been carefully configured specifically to make sure NPCs are spawned in a room before you enter it, but there are range limitations on spawners and a delay before an NPC is spawned so if you run through a POI like you're playing Doom you may not notice NPCs until they are already behind you.

NPCs clipping through walls and such is a game bug that we cannot fix.

I keep god mode active and just use it when a soldier is clipped into a wall hit G enter wall take him out then hit G again to turn off. Yeah you have to look up before going through doors you can usually see the edge of the turret before it can fire attach an explosive device to top of door boom no more turret.

Also, if you often find enemies spawning behind you: did you make sure to destroy all spawning pads?
Of course, you can't do that in case you are in a POI that is (still) shielded, but then again you can not achieve much in a shielded POI anyway.

And as the others said: if you are using god mode to get your backpack, setting "Keep inventory on death" to "Everything" might be the difficulty setting you are looking for.

Originally posted by Thegallowman:

To be specific, I'm doing the abandoned bunker because I don't know how else to get quantum processors.

To clarify: By "abandoned bunker," do you mean all the different kinds of abandoned POIs, or specifically the one actually called an Abandoned Bunker. If the latter, those are not the only source of quantum processors. All abandoned POIs except the two small ones on starter planets (Abandoned Workshops and Abandoned Pads) have them, and most of them are easier to run than the bunker. The only one that's harder than the bunker is the new Abandoned Assembly Yard. The rest are varying degrees of easier, at least in my opinion. The Abandoned Depot is the easiest (and shortest) abandoned POI that has quantums.

So, in addition to perhaps going into your settings to make it so that you lose nothing upon death (Which is my preferred setting), perhaps try different abandoned POIs to get your processors.

As for things spawning behind you: Things will sometimes "spawn behind me" in non-abandoned POIs that I raid, but that's because I neglected to notice a destroyable spawning pad. Until recently, there were no destroyable spawners in abandoned POIs, but there were/are a few invisible ones in some of them which will spawn twice. You eventually learn where they are and can then anticipate them. However, such places do not exist in the abandoned bunker, though there are a couple of spots that will re-spawn an infected Zirax or two once you have opened/cleared certain rooms. Again, you eventually anticipate them. A few of the abandoned POIs now have insect and horror spawners that will continue to spawn at intervals until you destroy them. The Abandoned Bunker also does not (currently, at least) have any of these, however. The newer abandoned Assembly Yard and Power Plant do, and they have been added to the Abandoned Reactor. I would not be surprised if they are also added to the bunker at some point, given that it's a higher-level abandoned POI and Vermillion likes to add new and interesting ways to die. :)

The abandoned bunker is one of the hardest/longest POIs. Try the abondoned depot or abandoned drone base. Those are quite a bit easier, imho. All of them are doable SP but takes some practice to find the right tricks.

Also make sure you have good armor, and good weapons. I use the minigun fired in short bursts to clean out bum rushes, and the light scout rifle for distant victims. The minigun is NOT good for longer range, it is a short range weapon, and don't just spray as the first few bullets will be near target but the rest will probably miss and waste ammo. Always reload it between "events" as you might need all 250 shots.

Originally posted by ZomBeGone:

...Also make sure you have good armor...

This^^^ Not only good, but in good repair. It does not take much degradation for the amount of extra damage to be noticeable, and given that abandoned POI tend to use swarm tactics, a little extra damage per hit will add up fast. And, while there is some debate about inflictions and armour repair, I can always tell when my durability drops below 80% as I seam to start getting debuffs with every second hit.