I have a question? if I get the welcome suica card can I link my online ticket purchase to that card?
It depends on what kind of “online ticket” you’re talking about. Presumably this is a Shinkansen ticket or long distance train ticket booked through Eki-net or Smart-EX? If so, you can link it to your Welcome SUICA. You might even be able to use it (as a “key” for your e-ticket) after the credit has expired as it’s not related to the credit on the card.