I think you will find that reasonable people may disagree on this issue. I fall in the camp that says tables are not a layout tool for me in html email just as in html for web pages.
I'm not really sure what you mean by css layers but the general problem is that many email clients including Gmail will strip the head section away so css in linked style sheets can't be relied on. Some will put <style>...</style> right in the body which may work sometimes but is not valid html.
Unfortunately the current state of affairs for html email is not great but I think the only way to have correct markup and reliable rendering is to use inline styles on each element that you want to style. I mean style="..." on every element, which is tedious and verbose markup but does work.
Images can also be used but many email clients may strip that out too so its best to make sure the message of your letter is contained in text so that if the user doesn't see the images it still conveys the message.
I'll be linking to some good resources about html email that I found in my research when I document this feature.