I believe there is no difference between TIG and Lugs in how the frame feels or reacts.
The tube diameters and the wall thickness and the length of the butt reinforcements will have effects on the frame's feel and reactions.
( and geometry)
A carefully built frame without cold setting so there are no in built stresses will give a sweeter riding frame.
Your last question. This question is a huge question. It will take 30 years to explain 30 years of experience
but to boil it down
I want to know your position data points. (attached drawing)
How to determine these data points? Some riders understand these, for some we must seek the position data with a biomechanical assessment (a big subject which I will not explain here),
also the position on the bike will change as the rider gets fitter, stronger, posture can change,
and then we all get older so things have to change.
"A bicycle is not a sofa"
all things have to be taken into the project
It is about the intended use for the bike.
and then I design the frame geometry to fit under you for the bike's intended use.
I select the materials.
I do use fragile tubes, there is no benefit in saving 100 grams and havijng a fragile frame, there is no performance gain. I long lasting bike for your hard earned dollars is important.
We speak and I explain my rational of design and choices.
Refer to attached sample CAD drawing.
Then the metal work will begin.
for me it is about
[FONT="]A bicycle that gives them many years of enjoyable riding. So with each passing year, their Llewellyn bicycle gives them greater value. Thus they Cherish their Llewellyn. That pleases me.[/FONT]
kind suggestion to the moderators of this forum....please put this post in the homepage....post like this one are not easy to find in my modest opinion....