The buff from Z ability on your team will be apply to all of your team with the same tag requirement and will multiply the base stats on each character. For example I have SP Purple Broly as the core then I have Shallot as the bench with 13% hp to Saiyan tag. That means if my SP Broly have 1 million base hp it will be increase to 1,13 million hp in battle. The calculation of equipment will same as Z ability if I put equipment with 3% hp to SP Broly then the hp will be increase 30k and then sum by the Z ability and base hp the SP Broly hp in the battle will be 1,16 million.
For the vanishing step. After you use blast card, for the last moment of your character throwing the blast ki you should swipe up like moving up your character to the front (by using this you will decrease time of the blast card animation) then swipe to left/right when your character being attack or use strike card to attack. If you still didn't understand go check youtube there is many tutorial of side step blast card.
