Configuration is purely managed through gamerules, here is a list of gamerules and what they do.
Player kills only
Gamerule: 'lifeSteal:playerKillOnly'
Type: Boolean (true/false)
Description: If a player should only lose health when dying to a player.
Default: true
Ban when minimum health
Gamerule: 'lifeSteal:banWhenMinHealth'
Type: Boolean (true/false)
Description: If a player should be banned when they reach the minimum health value
Default: true
Life Steal Amount
Gamerule: 'lifeSteal:stealAmount'
Type: Integer
Description: The amount of health that should be stolen upon death
Default: 2
Minimum Player Health
Gamerule: 'lifeSteal:minPlayerHealth'
Type: Integer
Description: The minimum health a player can reach (if the value is below 1 it is automatically corrected to 1)
Default: 1
Maximum Player Health
Gamerule: 'lifeSteal:maxPlayerHealth'
Type: Integer
Description: The maximum health a player can reach, set to a value of 0 or below to disable.
Default: 40 (20 hearts)
Player Maximum health is now stored via the maximum health attribute making it easy to modify and for other mods to be compatible with as long as they dont actively enfore their own max health values.
Heart
Hearts are a consumable item that give players who consumes them 1 additional heart.
They cannot be used to bypass the maximum heart cap if one exists.
Heart Crystal
Heart Crystals are a component used to craft hearts
Heart Dust
Heart Dust is a component used to craft the heart crystal
It can be obtained by mining Heart Dust Ore which drops on average 2 dust
Heart Dust Ore
Heart dust ore is a naturally generating ore that drops 1-4 heart dust when mined.
Heart Dust Ore generates about as much as diamonds but only between y = 0 and 40 and in veins of up to 3
This means it will be very difficult to find and cannot be found in deep slate layers.