Edgar could definitely take McGregor down - he'd probably get back to his feet fairly quickly, but Edgar doesn't care if people stand right back up, he'll just take them down again and again to win the round, force them to expend energy getting up, and hit them as they stand. He doesn't tend to shoot the kind of telegraphed blast doubles that fighters are used to countering with uppercuts , but prefers knee taps and ankle picks (takedowns that work especially well against a wide, low, bladed karate stance) woven into striking exchanges. Stylistically, he's an awful matchup for McGregor.
Mendes is more of a question mark. McGregor could probably outpoint him on the feet until he gets aggressive, then counter Mendes' counter, but if he's willing to brawl with him the same way he did with Holloway, Porier, and Siver, then he's going to eat power shots from Mendes at a range where it's easier for Mendes to generate full force than for McGregor. We haven't seen how well McGregor defends against clinch takedowns or body-locks yet (his high center of gravity does him no favors here), but if he lets Mendes get close, he's in serious danger until he can reestablish distance and slow down the fight.