Do you want potion  effects without the hassle of brewing potions. Well the effect command got you coverd. It's more powerful than any of the potion.

First you put /effect. Then you put your target. Then you put the time of the effect. 9999 is forever until you die. Then you put the strength of the potion. 255 is the max. Then put true.

Do these commands during PvP

/effect @s health_boost 9999 255 true

/effect @s regeneration 9999 255 true

/effect @s resistance 9999 255 true

/effect @s absorption 9999 255 true

/effect @s conduit_power 9999 255 true