Welcome to the forum!
You might want to take the time to read our excellent Official Sapienmed FAQ (Updated). (While you’re at it, check out our helpful forum search engine–that little magnifying glass icon in the upper right corner of every page of this forum.) These tools will help you find answers to commonly-asked questions and to help you get the most out of your Sapien fields!
Yes. The volume just needs to be loud enough so that you can tell if your field is playing or not.
Sure.
As long as the speaker is within your aura (an oval that, for most people, is typically the width of your outstretched arms). Some people feel that the closer the speaker is to the vertical midline of your body, the better. Other people are just fine if their speaker is off to the side (but still within their aura).
So, listen to what you’re saying here, which is “I know that its been said that its wise to X but I (for my own reasons) would rather not be wise and…?” Guess what? You get to choose! You get to do what you want to do.
When you read the FAQ, you’ll learn the guideline of limiting yourself to “4 fields for permanent physical changes” is because physical changes can be energetically taxing and permanent physical changes are the most energetically taxing of all. They’re energetically taxing because you’re using your energy to create changes in the “solid” physical world. And your fields will be affecting physical, biological and chemical processes with your body (which can affect other, unrelated processes in your body).
Now, might there be a difference if your fields are focused on one subject as opposed to 4 different subjects? Different individuals have reported different experiences, so it’s hard to draw a hard-and-fast conclusion that could apply to everyone (or most of everyone).
ETA: Since your thread title is asking about “Creating the best stack,” you might also be interested in our How to Create Great Stacks thread, too.