In an average booster box, how many LV Xs are there? I know in the ex series it was a preset number, varying by set, is it still like that?

japanense box are all the lv x of the edition (for example, buying the two dp4 box, you got all the lv x of the edition (except for the most rare lv x, in dp4 garchomp LV x that is more difficult to obtain but in his place you got another lv x (cresselia or the crow).

in dp5 boxes you get each of the lv x in the set. The only chance that you get 2 of the same lv x is if you buy the box where you can obtain the most rare of them (in dp4 is garchomp lv x and in dp5 a porygon z LV x). For example in the heatran box I obtain a uxie, a mesprit and a ryperior lv x, but in the regigas box i obtain 2 azlef and a magnezone lv x (no porygon z LV x). My friend also open a regigas box and he obtain a azlef lv x and 2 magnezone lv x (mo porygon z). In december I open a 2 moon hunting and a night dashing box and in the night dashung box i obtain glaceon, leafeon and a gardevoir LV X. In the first moon hunting box I obtain a honchrow, a cresselia and a garchomp LV x but in the second I obtain 2 cresselia and a honchrow. Friends and players of my city have the same experience and I recopiled the data and conclued that garchomp and the porygon z LVX are the rare cards of the set and obtain them are for lucky only. In american set in one box you can obtain (0-2) LV x at random. I hope that my answer can respond your question pikachu*

For use a japanense card in a tournament, you have 2 ways: 1) Get a copy of the card with the language of your area. 2) Get the card data book of this edition that has downloaded from www.go-pokemon.com. Remember, the game is Universal and the cards of all the locations are legal (obviously the cards distributed by pokemon and nintendo). I prefer japanense cards because are more economic, you obtain more rare cards in a pack and you have a 90% of chances to obtain all the LV x of the edition if you buy the 2 box of the set.