Very nice. I would put hardware cloth below your soil to keep gophers, etc. from tunneling in. As far as soil mix use the search feature and you should find a wealth of info.

lovely. If you do not want them to gray be sure and stain them soon.

Those are nice beds! I agree, put hardware cloth down if there is any concern for gophers or voles in your area. It's a tightly metal mesh that goes down before you fill the beds.
I filled my raised beds with a mix of about 1/3 manure and compost and 2/3 soil. Things grew nicely in them last year.

would the gopher protection need to protrude a little beyond the garden edges?

can you access spent mushroom compost? that is our preference.

len

Here is a link that might be useful: lens straw bale garden

I usually try to break up the soil underneath a new raised bed as much as I can. I then put down a nice thick layer of composted manure (horse/goat/chicken, whatever's available).
I have access to great compost/soil mixes from our landfill. Ours are certified organic. Not all are, or you can find a soil/landscaping type place that carries different soil mixes. Usually the "vege mix" has a good amount of compost that isn't too hot.ASK, though!
I top the beds with my own compost usually early spring so it has a chance to settle in before planting.
Every couple of years I get a truckload of the stuff from the dump to re-fill my beds. They do tend to sink and get a little hard IMHO. I usually churn it up with my weed weezle (or whatever it's called)in between plantings to fluff it up. HTH Nancy