Secondly, car seats Maxi Cosi Pebble vs Cybex Could Z?
If compactness is still your main requirement, I would definitely still stay with the Mios as the Egg, as the Egg is super heavy to be honest and bulkier than it seems. If, however, you'd be ok with that extra weight and size, the wheels are definitely chunkier, better for bumps, and the stroller looks gorgeous. I personally would probably stay with the Mios though.
ABout car seats, I personally don't love the Cybex car seats as much; they are heavy (the Cloud line especially), and although the positioning is a great thing to have, you cannot recline the Cloud car seat during the ride, which is a shame and puts me off of this brand. So I would rather go for the Pebble, I myself had one, and it is so much lighter, and the materials so much softer (had a Cybex before a Pebble and my son was constantly sweating in it, even if it was the higher line). And if you'd want that recline, the Kiddy Evoluna or the Joie i-Level can be positioned during the ride, which is the healthier thing to do, so I would rather look there.