First of all: Every Board sounds different and better/worse is highly subjective. So dont expect to boards to sound the same…however you can change the sound alot through mods. But to answer your questions:

1. As stated in my original post i used the Case Foam the Case came with and added a layer of Neoprene (1.5mm Thickness) that i bought and have cut to size myself. Other then that i only used the standard Foam that comes installed between PCB and Plate
2. For the tape Mod you just stick one or two layers of tape on the backside of the pcb. Just sear “tape mod” on youtube and you will find a tutorial without a problem. Its a pretty cheap and effective mod to deepen the sound of a keyboard.
3. Perhaps someone who did play around more with the standoffs of that specific case can help you out with that question. Generally spoken: Installing the standoffs gives more points were you screw the PCB into the case…which reduces flex what obviously leads to a harder typing feel. It changes the weight distribution and can affect the sound in certain areas of the board. Depending on the mounting style (for example if you use O-Rings) it can also lead to more noise from the pcb making contact with the metal of the standoffs. Most people like to dont use additional standoffs, like the Alumaze Kit provides them, and dont install them. Also when screwing the PCB into the case you should be aware that how much you tighten the screws can affect sound and typing feel. I would encourage you just to try around and look what works best for you. I think it will matter a little less given that you want to use the PC Plate (which i couldnt because Wooting doesnt produce them in ISO layout).

Hope it helps. If you want more opinions i saw that there is a pretty substantial video from Badseed Tech on youtube, that goes into detail about the setups and comparisons between the cases and mods, with a lot of sound tests. Might be worth checking out for you.