Welcome Back...:-)
1. What brands are best?
i had an aquapod 12g which i really enjoyed, currently have two 29g biocubes...i think both are good tanks.
2. What are the pros and cons?
Pros it is All-in-One, there are so many modifications you can do...nano-reef.com has a lot of ideas
Cons..some space limitations...learned this the first time...go with small frags to watch them grow
3. I had planned to go cold turkey out of the hobby, but this is killing me! Can I mount one now and still move it?
Yes...much easier then moving a big tank...:-)
4. Could a blenny live in a 24g biocube?
I have a canary blenny in one of my 29's so I say yes.
5. How well do these all-in-ones keep the parameters?
Agree, with the earlier statement..as long as you maintain your maintenance, parameters will be fine.
6. What corals could I have? Advice, pls, friends?
Depends on what lighting you go for...with just the stock lighting...some LPS, zoas, leathers
7. My goals would include keeping a couple of LPSs, a fish or two (I'd adore a Midas and ... something to keep it company... ideas?) and really that's about it.
I think you will enjoy your date...and come back with an idea of what you want. If you do find one that you really like I would check some forums to see if there are any for sale.
Good luck in your search.
Mike