The tech community in Anchorage is small and consists of about half a dozen divers. If we're talking about active technical divers, regularly doing proper trimix dives with 50% and 100% deco gasses; it's two people (myself and one of my buddies). There's a slightly larger group of GUE trained (recreational) divers, maybe a dozen or so that are active. You tend to run into the same small group of people if you're diving regularly here and everyone knows everyone.
I've only been technical diving in Anchorage for 5 years, and my ability to do so is limited mostly by buddy availability. Gas logistics are easy enough (I fill in my garage), but helium is expensive (last invoice: $1.43 per CF for UHP). Oxygen isn't so bad (last invoice: $.26 per CF for ABO). That puts my cost of 21/35 at around $.46 per CF, and I'd expect to pay double that in a retail setting. I primarily dive off my boat or buddy boats, but there are two 6-pack dive charters in Seward now that do one heck of a job (and have either a 2 or 3 passenger minimum). Both boats are fast and can have you on some great sites in 30-45 minutes.
Not much for wrecks in Southcentral Alaska. There's an old barge in Resurrection Bay that's fun to poke around in a couple times a year. One wooden steamship wreck in Prince William Sound that's almost unrecognizable. Rumors of other wrecks, but they're hard to find - usually because they were either wooden, or because they sank deep. Southeast Alaska is better for wrecks, but still just a few of them.
Steve Lloyd is the man to go to about wrecks in this area; though he's working on leaving the state.
The technical diving I enjoy consists mostly of deep walls and boulder fields. The fish life and invertebrate life on these dives can be amazing; more plentiful and larger than what we see shallower. A few species don't really care for the shallower water, and you'll see them down deeper. I almost always see lingcod when we get deeper, and usually big ones (4-6'). We found a site last spring that has a plumose anemone field at 130' that would be measured in acres. It's huge. I'm sure there are more great sites out there, and we're actively looking.
One concern with technical diving in Alaska is the lack of a decompression chamber in the State. Closest one is in Seattle and with transport times ranging from 6-24 hours, things start looking pretty grave when you consider the impact of a serious DCS hit. My buddy and I tend to be extremely conservative with deco as a result.
All that said, most of the dive sites here can be dove quite comfortably on recreational profiles. 32% in a set of doubles will take you quite a long way.
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