I wish there was some directions I could give you on the first question. A lot of it is trial and error is getting them to align just right. Sometimes a layout container can be helpful. This might be a good topic to add to the Ideas section.
In terms of the second question, my best advice is to set the axes to be fixed.
Like Tracy, I wish there was a concrete direction I can give. My suggestion is to 1) plan out where everything will go in your dashboard then 2) definitely use layout containers, and 3) if you can, fix the dashboard size so you can also fix the size of everything else. I still don't understand how Tableau chooses which containers to resize where.
In regards to fixing the axes, there are a couple of methods: One is that if you use Measure Names/Values instead of separate worksheets for each measure, all the axes will have the same range. An alternative that I learned from Andy Cotgreave is that you can use either fixed values or calculated fields to set up invisible reference lines for the min/max. Tableau will automatically resize the axes to accommodate the reference lines.
Jonathan, is there a thread with Andy's suggestion somewhere on the Forums? I'm always looking for ways to trick Tableau into making the min and max of graphs somewhat dynamic, but not necessarily fixed...
I'm not sure whether it was a forum post or a twitter discussion, honestly,, and can't find the original reference. Generally I'd use some sort of aggregate calc, for example using a WINDOW_MAX() to get the maximum value in the data set, put that on the Level of Detail shelf and then use it for the reference line.
Thanks everyone - I will try using fixed containers etc with the dashboard. With the axis I will try the reference line trick.
Just gone back to implement this. Used the invisable reference line, also added a parameter so I can make it dynamic. It's a great solution - thanks for your tips.