Be careful: in the mod I check for negative values only, which means you're free to break your game by high values.
The mod doesn't mess with your savegame directly and doesn't write any mod-specific information on save. Yet it is possible that you can botch your game with some settings.
So it is not necessary, but it is still highly recommended to make a backup of your savegame (stored in %UserProfile%\AppData\LocalLow\Lazy Bear Games\Graveyard Keeper). Especially if you're going to change timescale or energy replenishment.

Pricing
InflationAmount
Default: 1 (normal)
The multiplier of the amount of coins that is added when you buy a significant number of the same item from a vendor.
0 means that the price will stay the same (10 berry pies will cost you solid 35*10 = 3 silver and 50 copper coins)
negative numbers will make you feel a wholesale buyer (yet don't make it too low, I recommend to keep it beyond -1)

Menu
DullInventoryMusic
Default: false
Dulls the music while you're in tabs-GUI (inventory/tech/quests/map).
The option is for those who just miss the feeling that the game is paused.

Timescale settings
TimeMult
Default: 1 (normal)
The ingame time multiplier. Might be unstable.
The value 0.75 will make one ingame day equal to 10 real life minutes. The value 0.00521 will make one ingame day last for 24 real life hours (roughly).
Values beyond 2 will cause npc's to skip their posts, making the game nearly unplayable. Beyond 4 are absolutely unplayable. Values below 0.001 are considered invalid and the default value (1) will be set.

SleepTimeMult
Default: 1 (normal)
Sleeping time multiplier.
SINCE 0.7: The amount of HP/EP regenerated is now affected by this setting, so you'll sleep the same amount of ingame time (thus, having SleepTimeMult set at 2, the sleep would actually take twice less seconds, skipping the same amount of ingame time and restoring the same amount of HP/EP)
SINCE 0.6: It just multiplies the sleeping speed, which is 2240 times faster than real life (24 hours would take 38.6 seconds).Therefore, if you set this parameter to 2, it will take 19.3 seconds to sleep for 24 ingame hours.
BEFORE 0.6: The overall time speed would be (original sleeping speed * TimeMult * SleepTimeMult). Thus, if you want the ingame time to pass by slower, you would probably like to set SleepTimeMult to something inverted to TimeMult (e.g. for TimeMult=0.2, you will need SleepTimeMult=5 to maintain the original time speed while you're sleeping).

Sprint settings
DefaultSpeed
Default: 1 (normal)
Your character's walking speed multiplier.
Values beyond 3 are not recommended.

SprintSpeed
Default: 2
Your sprinting speed multiplier (normally it's higher than DefaultSpeed, since it applies to the original speed, not the DefaultSpeed-ed speed).
Values beyond 5 are not recommended.

SprintKey
Default: LeftShift
The key that activates Sprinting.
You can set any value that is a valid Unity KeyCode enum constant name.

SprintToggle
Default: false
true - toggle sprinting with SprintKey
false - hold down SprintKey to sprint

EnergyForSprint
Default: 0.1
Energy cost for sprinting per second

Health and energy settings
DmgMult
Default: 1 (normal)
Player health damage multiplier.
greater than 1 - more damage (harder)
lower than 1 - less damage (easier)
0 or less - invincibility

GlobalDmgMult
Default: 1 (normal)
Health damage multiplier. Unlike DmgMult, it applies to ALL beings and BEFORE their armour check.
Thus, the values lower than 1 will make armour stronger, and values higher than 1 will ignore more armour.

RegenMult
Default: 1 (normal)
Health regen multiplier.
greater than 1 - faster healing
lower than 1 - slower healing
0 or less - forbidden (the default value will be set)

HealthRegen
Default: false
Toggles health regen over time.

HealIfTired
Default: false
False - healing with HealthRegen will stop if your energy level is below 10%.
True - HealthRegen will always apply.

HealthRegenPerSecond
Default: 0.5
Amount of health regenerated per second. This value is not affected by RegenMult.


EnergyDrainMult
Default: 1 (normal)
Energy drain multiplier.
greater than 1 - faster depletion (you become tired faster)
lower than 1 - slower depletion
0 or less - no energy drain

EnergyReplenMult
Default: 1 (normal)
Energy replenishment multiplier.
greater than 1 - faster replenishment (also, you sleep less)
lower than 1 - slower replenishment (also, you need more sleep)
0 or less - forbidden (the default value will be set)

Technology orbs drop
OrbsMult
Default: 1 (normal)
Tech orb drop multiplier. After applying, if the result is not integer, the amount of orbs to drop will be rounded to top (if RoundDown is not set to true).

RoundDown
Default: false
Round down the result of orb mult.

OrbsConstant
Default: 0:0:0
A constant addition to every orb drop. Applies before OrbsMult.
The values are Red:Green:Blue.
Only integer values are valid (no dots!)
Negative values are valid: in that case, orbs will be subtracted from drop amount.

OrbsConstAddIfZero
Default: false
Whether to add the number of orbs from OrbsConstant if the initial value is 0.
For example, when you chop trees with OrbsConstant=1:1:1, you will get blue orbs if this parameter is true, and you won't get blue ones if the parameter is false.

Interaction speed
CraftingSpeed
Default: 1 (normal)
Crafting speed multiplier (workstations only).
If you want crafting to be instant, use some value near 20.

InteractionSpeed
Default: 1 (normal)
Interaction speed multiplier (all interactions, not fully tested yet).
Multiplies the CraftingSpeed as well, so there's no point in high CraftingSpeed if you've already set InteractionSpeed to some high value.
Values greater than 5 will make interactions really fast, values beyond 10 are not recommended.


Example of orb drop settings:
Let's say, in your config file you have lines as follows:

OrbsMult=2.5
OrbsConstant=1:0:5
OrbsConstAddIfZero=true
RoundDown=false

After chopping a tree that gives you 1 red and 1 green orb, you will receive:
(1+1) * 2.5 = 5 red orbs
(1+0) * 2.5 = 2.5, which rounds to 3 green orbs
(0+5) * 2.5 = 12.5, which rounds to 13 blue orbs

Another example:

OrbsMult=1.5
OrbsConstant=2:-2:5
OrbsConstAddIfZero=false
RoundDown=true

After chopping a tree that gives you 1 red and 1 green orb, you will receive:
(1+2) * 1.5 = 4.5, which rounds to 4 red orbs
(1-2) * 1.5 = -1.5, but we cannot take orbs from you, so you'll just get 0 green orbs
blue orbs won't drop since OrbsConstAddIfZero is set to false