I have practically no experience with a pulse arc welder, but I do have over 20 years on lasers.
I did do a short seminar at Stuller, on I believe an Orifin(?)
I was very impressed at what a pulse arc machine can do, and with 2 reps watching over my shoulder, offering advice on the settings, I sucessfully rechanneled an Opal inlay, Sterling ring. The 2 technologies are in some ways quite similar.
Having said this, welding fine chain is problematic on the laser, and I would expect it to be more so with electric arc.
My suggestion would be to use the torch for this application.
If solder is first applied to the fine chain, and then the heavier item wbich I am attaching that chain to is heated until the solder on the chain flows toward the heated, heavier piece, the chain is less likely to commit suicide, while making a good joint.
Just my opinion.