I've played a pretty good ICs here in Utah. He didn't have the chaingrabs down for Link yet but he's beaten top players in the state (who use more expectable characters rofl), so I feel I've got a pretty good rep here. I tried playing him on FD and I'd say it's a -3. Link really has no options but to camp the edge or try to bait ICs into projectiles. When I would make it back onto the stage, I had a hard time trying to outplay him at all.
That said, even on FD sopo is probably the easiest character to beat I've ever played. Sopo doesn't have good approach options or good counter-spam options. Also, easy and kinda fun to edgeguard against. Whenever Link can get the ICs out of sync, away from each other, or sopo, the MU is probably +2 or 3 in Link's favor. His only real option when alone is to try and chaingrab>fsmash and quite frankly Link laughs at that. It's the perfect angle for DI and Popo can't edgeguard Link effectively. Nair or Uair can KO Link at high percents, but a Sopo who has Link at high percents is a sopo who's been doing his CGs wrong.
On regular stages (since any decent person would ban FD) I'd say it hovers somewhere between -2 and -3. ICs' regular spam game loses to Link at medium or long distances, and it messes with their synchronization, usually knocking Nana away and ruining the camp setup. This is a MU where Link comfortably outcamps, period. However ICs can counter Link's spam game through platforms with nairs/uairs and eventually force some sort of other option out of Link, even on BF. Even fancy or clever mindgames can only do so much before a patient IC player can grab out of it, and even when Link knocks Nana away it is usually close enough that Popo can wait for her to get back, even with button mashing. Essentailly, once they get in close, they win, and that is where Link's main flaw comes in--he can't zone them well enough to keep them away.
