<includeonly>=</includeonly>==Adjustment for Competitive Battling==<includeonly>=</includeonly>
I have mentioned that IVs give a total of +40 total points spread out amongst the Yo-kai's stats at Lv99 (double points for HP). I have also mentioned that Attitudes grants +30 total points, either all in one stat or split evenly into two stats at Lv99 (again, double bonus to HP for each point in it). These are the Lv99 stats - since competitive battling is set at Lv60, you will receive a fraction of these bonuses. By messing with the IV Calculator I noted that you can benefit from a total of +26 out of the +30 EVs, which of most of them - however, your Yo-kai must have earned them all in the single-player game! They will NOT be automatically given by the game when it sets their level to 60.
As for IVs, not sure how much of the bonus you get - likely 60% of it.