If you want to dual-box you have to link them to each other.

Alt 2
^
|
Main->Alt1

Won't give you any RAF bonus.

Honestly, if you want all the classes the most efficient way is going to be to set them up in a line and use some WOW Classic/free months and TBC trials.

You can set something up like my signature where you level them to 31.99 and then gift to 60, level the next account in the line to 31.99 and gift to 60 and so forth.