No difference. You are cooking the shallots/tarragon/pepper down in wine and vinegar until sec first. Using the same pan, you add a couple drops of water, add yolks, whisk, add butter.
But Hollandaise is a mother sauce. You need to taste the benchmark Hollandaise first, and then add other stuff for bearnaise, or choron, or whatever you want.
I'm not sure what you mean kuan, but to my palate there's a difference between letting shallots and tarragon infuse in wine and emulsifying that wine in your sauce, vs making a sauce and adding diced shallots and tarragon at the end. Just like there's a (rather large) difference between adding crushed garlic to mayo vs emulsifying garlic in oil to make aïoli. In fact I like to infuse some of the shallots and tarragon in the vinegar AND add some bits of diced shallots and tarragon at the end. They both bring their own thing to the table in different ways.
I know the "mother sauce" concept can be debated to death... personally here's how I see it:
• Hollandaise is a mother sauce for sauces like Foyot, Maltaise, Watercress, Mousseline, etc...: classically, you make a batch of Hollandaise and add ingredients to make those sauces.
• Hollandaise is NOT a mother sauce for sauces like Bearnaise, Paloise, Raifort, Choron etc...: classically, you can't start those sauces from a batch of already made Hollandaise.
• Mayonnaise is NOT a mother sauce for Aïoli: you can't make aïoli from already made mayonnaise.