Welcome! When you repot, you can bury the roots growing in the air but if some won't go in the pot it is ok to leave them out. Sometimes the roots grow too high on the plant or they grow upward so if you tried to bury them in the pot they would break or won't fit. So just leave those ones be. It looks like you do have one growing upwards so if you tried to bend it down it would break it. Just mist the air roots and water them too when you water the plant.
Like the others said, pick a pot that just fits the healthy root ball. Orchids do not like to be over potted. It will cause root rot because the meadium won't dry out fast enough. You might even be able to reuse the pot it is in if you need to cut off any dead roots. Cut any squishy or hollow roots off because they are dead.
Orchids can get top heavy. I usually set the pot into a bigger clay pot to stabilize it. I like the clay pot to be a little bit bigger so there is a space in between the two pots for air flow.
It sounds like you have Phalaenopsis hybrids. Do they have a tag in the pot that says the plants hybrid name? If they don't you have Phalaenopsis NoIDs. It means they have no ID and you dont know the plants parentage. To answer your question, Phal leaves can look different in size, shape, and color. It just depends what their parentage is.
When you repot buy a bark mix and soak it for at least 24 hours. New bark won't hold water like old bark does so you will most likely find that you will need to water more but it all depends on your growing conditions. If you have a hard time finding orchid supplies where you live, Lowes and Home Depot sell a bark mix called Better-Gro Special Orchid Mix. My Home Depot doesn't always carry it but I always find it at Lowes. I just bought a bag for $6. It contains fir bark, charcoal, and perlite/sponge rock. Do not use Miricle Grow Orchid mix! It is way too soil like containing mostly peat and it will suffocate the roots. I prefer clear plastic pots so I can see the root system and Phals photosynthesize through their roots if they are exposed to light.
Good luck and if you have anymore questions just ask! There is a great thread about Phals bought at grocery stores and big box stores and Phals in general called The Phal Abuse Ends Here. It is long but has a lot of great information. I recommend reading it. Here is the link.
http://www.orchidboard.com/community...ends-here.html
Here is a link that explains why a NoID is a NoID just in case you want more info.
http://www.orchidboard.com/community...noid-noid.html