Conor has shown more effective linear/straight kicks than Pettis has while Pettis has the better lateral/round kicks. Pettis has more dangerous kicks but Conor's can add up quickly and allow him to set up his boxing as well. They're not just flashy, as he proved in the Mendes fight. He was landing spinning back kicks and front whip kicks to the gut at will, one after the other.
Pettis was crowded by RDA to take away his space to kick but even that isn't foolproof. Conor will only need his feet set for a split second to launch a spinning back kick or jump spinning back kick, as he's been drilling to use against RDA in at least one video. His TKD instructor is holding the pad and pressing forward, crowding him, where Conor pushes off of him with his forearm to create enough space to launch his jump spinning back kick. You don't necessarily need to push off the aggressor who is pressuring to take away optimal kicking range at all if you can throw a spinning back kick as quickly as Conor can, since your feet only need to be set for a split second to do it.
Here is Conor drilling what I just described
In an actual fight he'll be going all out for speed and not just drilling the technique, so it'll be much faster than in practice. At a major US university he was tested and his hips were clocked at a rotational velocity of about 800 degrees per second which is insanely fast, only two or three tenths of a second slower than his jab. This was faster than Vitor Belfort's spinning back kick that knocked Rockhold out and faster than Rory McIlroy's golf swing, who held their previous record of around 720 (IIRC) degrees per second in angular velocity.
If a fighter takes away your space to kick then you either attempt to take it back long enough to launch the kick or you launch the kick immediately once your feet are able to be momentarily set, even if you only have a split second to do it. So, pushing a kicker back by crowding them is very effective but it isn't foolproof and you'd have to be on them so tight you'd have to give them no way of getting any space at all to spin and kick when only very little space is needed even in tight close quarters. Conor won't have to leave his kicks at home, especially not ones he uses that are aimed at the legs to help him control distance (ie., his lowline sidekick, oblique kicks etc). Aldo ate a lowline sidekick seconds into their fight and he's a lot quicker than RDA is. The aggressor/pursuer also risks getting caught hard on the way in to closing the gap and a spinning back kick can at the very least hurt them and can knock a fighter out when it's aimed to either the head or body especially if they run onto it.