A couple random notes on tumblers:
You can't have too big of a tumbler (within reason). If you have a big tumbler, you can always just tumble one case if you want to. But, if you have a small tumbler and need to tumble a lot of brass, you will have to do it a little at a time.
Not all tumblers are created equal, although I haven't made any kind of a study of this. I used the same tumbler for years. I bought it from Midway. I came across a deal where a guy was selling basically a complete reloading set-up really cheap because he lost his job. I wanted the press, so I bought it. A tumbler was also part of the deal; it came from Dillon Precision. The Dillon tumber seems to have a much more aggressive action. It looks like it turns the media/brass over much faster. On my old tumbler the media seems to just shake. The new tumbler looks like the media is flowing almost like liquid. The result is that it takes less time to get really clean and shiny brass from the new tumbler. And the new tumbler holds more brass than the old one.
I personally don't like tumbling brass. My loading equipment including the tumbler is located in my house. The tumbler is loud and gets on my nerves. So, if the more brass can be tumbled faster, then I don't have to run the tumbler as long to achieve the same results. This many not apply to your situation but it is something to think about.
If I had it to do over again, I would buy the biggest tumbler available.
Decrimping. I am assuming you mean primer pocket crimps ?
I don't get a lot of crimped primers, but run across one now and then. I use a case deburring tool like you use to deburr a rifle case after trimming. If you have a large volume of crimped primer pocket cases, Dillon makes a tool for that purpose that I have often seen recommended. I wouldn't use it enough to justify it's price.