Several questions, mostly regarding character transfer

[worldofneil]

Sorry, but you can't merge service accounts or move a character from one service account to another. Although I don't work for SE, I've seen the same questions asked many times over the past 3 years and never once have I heard of it ever happening, sorry! You can do things like request a transfer of service if you put it on the wrong account (like Heavensward if it was applied to wrong account for example), but nothing like what you're asking.

Regarding changing worlds, when you put in the transfer request it checks at this point if the name is already taken on the server and if so will force a name change when you actually login. So you will need to rename (for actual money from mogstation) your existing character first, or delete it. Then do the transfer. As long as your character name isn't on the banned list (which is apparently constantly expanding, but doesn't affect existing characters), it should let you keep the old name. Or you could just transfer it and be aware it will make you change.

Oh and the transfer fee is the same regardless of legacy status, sorry!

Edit: I know you didn't ask this, but just to clarify in case you're not aware, but if you want to play with a character on service account 1 and also characters from service account 2, you'll need to pay 2 separate subscriptions each month (as well as buy expansions twice etc).