Excuse me as I'm doing this from the top of my head and not referencing a II/II+/IIe in front of me...
The Apple II Series has 8 slots - numbered 0 to 7. (The IIe has 9 - 8 + that RAM/Aux Slot but we are not counting that.) The PR# command works based on the slot number you give it. Pr#-ing to anything greater than 7 should do nothing or should give an error (depending on the Apple Basic you are using).
Slot 0 is usually the Language card, but without a language card, it defaults to keyboard and video.
Slot 6 is usually the Disk Drive card and nearly all software makers recognizes it as the default Disk I/O Slot and their programs point to it. It is rare for a program to ask for where the Disk Drive card's location.
Slot 1, 2, 3 & 4 is usually a printer/modem card - parallel or serial.
Slot 7 is usually for a second Disk Drive card, like the Apple 3.5in drive card.
Slot 1 & 2 are also used for C\PM Cards if they have it. Later on when they were made, RAM Extension cards were put there as well though these cards were rare. They pushed the Apple II to 64k to 512K of RAM by bank switching. Problem was there no absolute standard to bank switching so there was little to no support for them. There were a couple of RAM Disk programs that used them but they were proprietary to the card.
Slot 3 in some cases there was also 80 column video cards that went in there, again, like the RAM Cards, non-standard. Not until Apple made their own and made a standard for the IIe.
Slot 5 is where many put experimenter cards in like EPROM Programmers.
Given all that, people tend to put cards where they wanted because to them it either looked good or it made some logical sense to them. Because of that things did not work out because the software assumed that cards were in another place. So in the minimum - the Disk Drive Card should be in Slot 6.
Looking at your EZRAM II Card, it looks like it has corrosion on the last to pins on the right. Somebody might have put in backwards into the slot at one time it would do that before frying out. And J1 on the left is a fuse. Check it with a multimeter, if somebody did put in backwards, it would have blown to save the card and the Apple IIe. So if the card is not working, chances are that J1 is blown. If you get 80 columns when you PR#3, then it should be fine but boot up ProDOS and Apple Works - that will tell you how much RAM you have in the Apple IIe, including the EZRAM II.
When you PR# to Slot 6, when you have two drives on the card, it should access Drive 0 for a while first and turn it off, and then turn on Drive 1 for a second and then turn it off. If it is just 1 drive on the first port (Drive 0), it will access that one drive and that's it. If it is in the other port without a drive in the first port, then it wont access the second drive because it is expecting a drive in the first port.
The AUX Slot in the IIe is tied to Slot #3. So putting a 80-column/RAM card in there and giving the command PR#3 will activate 80 columns. PR#0 should bring it back to 40 column. You should be able to test that on the IIe. So if you have an 80column/RAM Card in the AUX Slot on the IIe, there should be nothing in Slot 3. If you have a card in Slot 3, move it to another slot or else you will have software conflicts between the two cards.
That's it as far as hardware is concerned. I need to think and look over my Apple IIs for the software side of the equation, which will be my next post.
Before I forget - look at your IIe's CPU. It should say either 6502B or 65C02. If it is a 65C02, then it is an Enhanced Apple II and boot up with "Apple //e" If not, it should boot up with "Apple IIe." If it has a 65C02 and boots with "Apple IIe" then somebody swapped out the CPU but not the ROMs.