OK so, I don't know enough about this (utilizing an IF output) but the FT710 is a stand alone SDR, as per everything Yaesu says. I believe the IC7300 is also a stand alone SDR.
Now say I connected the IF output to the antenna input and tuned the FT710 in my case to 455 khz. Would I then do main tuning from the rig outputting its IF?
The previous owner said they used it to output into a synchronous detector for AM on MW and SW. They also said it is useful for a panadapter. With the FT710 I don't need a panadapter but is that all a 455 khz IF output is good for?