Sorry for the late reply, I don't think there is a strategy at all for opening untamed packs as they are pretty straight forward. They contain 5 cards with at least 1 of them being a rare card or better and the timing of opening them does not matter. You can also open them using potions which increases the chance of legendary or golden drops but I have no clue if they are worth it (I personally never bothered with those).
I hope you'll enjoy the game, I leased a bunch of cards to you some days back which should help get to give an early game edge getting you a bit higher in the rankings.
If you have more questions on the game feel free to ask. I'll be writing some more posts about it in the near future.
RE: Jupiler League Week 26 Sunday Previews