Water yield % is not the same in the entire region. It has splotches, where the yield is bigger and splotches where the yield is lower. But in general regions do have a max value the yield can be.

So if you are careless where you put your wells, you might end up with higher yield of water in a more arid region, than in the less arid region.

Here you can see the different zones and their yield:

https://kenshi.fandom.com/wiki/Environment

Well Efficiency:
The Burning Forest is 100%,
and the Swamp is also 100%.

The actual exploration:
Amount of groundwater: Swamps 209;
If the burning forest is around 188

So (including production speed) The resulting water production is Is it different? Is it the same?
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* I'm confused because of 100%.

If it is 100% “for groundwater”, Water production will vary.

If it were 100% "explanation of max values" it would be the same.

Which of the two applies to you?

A = B (well)

but A =/ B (environment)

so what is fact?
A > B ? or A < B

100% just means there is enough ground water to fill any amount of drawing.

The actual amount a well draws, is dependent on the worker, amount of electricity and the fact how good your well is.

If well, worker, %. and electricity are identical in both locations, then they should yield same amount of water.

But if the % is the only difference, then the one with better % wins, when other values are identical.

But, again, the entire region is not of the same %. It varies, a lot. So moving well location 5 meters might drastically change your yield.

In my opinion, there is no area where it can exceed 100%.
So what about environmental variables?

100% okran green area vs.
100% of most swamps

However, the actual amount of groundwater is Swamp comes out at 209. (exploration)

Okran will be different.
It will be less than 209.
When everything is the same,

Who will win?
Or will it be the same?

Same example Fishman Island vs. Swamp?

Environment, groundwater (209, 233).

👆 Assuming everything is the same except for two.

Near Shark vs Near Fishman Island

what is a winner?

Too many variables and randomization to be more than a philosophical speculation. That said, Fisherman Island, when you settle to a random location.

Shark is in swamp region, but it has a 10% minimum with a multiplier of 2 and Fisherman Island has 30% minimum with 1.2 multiplier. So if you are lucky and find a 100% spot in both Shark wins. But if you want water near a specific location and you have to pick a random well spot, Fisherman Island is better. Multiplier is how much more each better well yields. And naturally added to this the worker's skill is also a multiplication factor.

Electricity? Since the well max level consumes 10, isn't the production the same as long as it stays above 10?

Water production from a well with electricity of 100 and
Is there a difference in water production from a well with electricity of 11?

Yes it is the same if it stays above ten. BUT if you are using 100% wind power, one must also take into account the wind generators do not constantly put out the same amount. You might also end up in a situation when an ore processor hogs all your electricity and there is none left for the well.