Can we discuss "Fallaway"?
 

Fallaway is something that has constantly confused me. I understand how to set it and test for it. However:

If the fallaway is set too slow, how does that affect handling? What does it feel like?
If the fallaway is set too fast, how does that affect handling? What does it feel like?

Can one or the other scenario be more dangerous on the road?

Long ago, the bearings were ball. They were set rather tight. Tapered rollers can live with a small amount of clearance and actually last longer. Just talking a lubrication gap here. So just zero to .0005 play. So you cannot fill it.
However set like this in a Softail, it makes the bike free. You can snatch a hand full of turn. Does not over steer on the interstate in windy condition.

Too your point, make sure you read the procedure. Some Harley's have finially been engineered to allow a torque. Some like my Softail have a hole in the fender for a plumb bob. Some from the front. Some have that crazy rock back and forth. All to confuse so you pay the man to do it.

As a closing, set it to the minimum and try it. With mine, it says 1-2 inch. I set it 1... I checked bearings while back. At 50k, they still looked new.

Oh, I understand how to set it. What Im looking for is what the bike feels like if its set too fast or too slow. Does it become lazy, does it drop into a turn faster, does it become harder to push into a turn etc...

Mine was set too tight from factory. Sure in tolerance but as i tinkered on more and more Harley's, I realized even a Fatboy could be more nimble. Even though mine has a slower setup, set to minimum fallaway, it is easier to turn and self centering.

It's simple. Too fast (loose) and you'll get a little "clunk" on bumps or when applying the brake. Too slow (tight) and it won't self center properly. Personally, I would never run a headstock bearing without some preload. The hammering from the road irregularities will shorten the bearing life.

Ride to check, adjust as wanted :)

I've ridden mine with a variety of fallaway situations... If it's really too loose, there will be actual play in the neck (which can/will become dangerous, and can/will damage bearings and races as they slam into each other). It's obvious when it's this loose, as it will klunk on bumps and you may be able to feel play with the wheel off the ground. If it's tight enough not to klunk but still towards the "too loose" side, you can get some handlebar shake. On my bike, if I go straight at 50mph, take my hands off the bars and let it coast down, at about 40 the bars start shaking noticeably. If it's a bit on the "too tight" side, the steering feels notchy rather than smooth as you turn the bars, and doesn't always respond as intuitively as expected. Personally, I like the steering feel when it's on the tighter side of acceptable, but not yet feeling notchy. I can ballpark this on a stand, but I usually have to make a small correction after the first ride.

Doc Harley has a good video on fall away and checking your front end

I think people are missing my actual request. I know how to do it, checking and setting it, I want to know what the riding feel is actually like based on the different settings: too light or too stiff.

I see from what has been said exactly what it fills like. However, no one is saying too light or too stiff. I am pretty sure everyone is setting it to the tolerance given. Since you say you know how to set it, set it. When you set it, set it to low figure. Then crank it around to high figure and note the amount it takes. Now dial it back to low and try it. If you don't like it,. crank it up half way up and ride. Then maybe all the way.

I know when i first set mine to 1", I thought it was way too loose. After a day, i will never go back. Now i don't ride without hands and i also seldom if ever go over 65. My Harley is not for that sillyness.