Brakes 1995 3.8 - What kind of bubble flare??

Well, it's past the weekend, not sure if you have your answer.

I'm not sure about your particular tool, but mine has different dies for bubble vs double flares.
Yours looks like it's truly making the "part 1" of a double-flare operation - more "flat" at the top and ready to be pushed into the tube to form the double-flare.

This is the tool I have: Amazon product ASIN B00AOTBVJQView: https://www.amazon.com/Cal-Van-Tools-165-Master-Flaring/dp/B00AOTBVJQ


The black dies are for the 1st step of a double-flaring operation.
The chrome dies are for a bubble flare.
The chrome ones have a different shape, and result in a more pronounced bubble.

The brake lines are 3/16".
A 4.75mm die should fit a 3/16" line, 3/16" is ~4.76mm.
In my kit, a 4.75mm bubble die is provided, no separate 3/16" since they're close enough, and as bubble flares are generally sized metric.

I wouldn't worry about whether or not the tool pushes into an existing, used flare, or the shape of that flare. Those are crushed to some degree on installation. As long as the die fits nicely into your new brake line and has the right shape the result will work.

The diagram below is handy - SAE fittings (like 3/16) will result in a single flare like the one at the left.
DIN (metric) fittings (like 4.75mm bubble) will give you a fitting like the one in the middle. Yours looks like that to me.
You'll notice the fitting is shaped a little differently to accept the different shape of the formed line.
The 3rd picture is a double-flare, those are pretty much the same on both.