OP, yes, shift to the smallest COG on the cassette, then remove wheel, if you have a SRAM RD, it most likely has a lock to lock the cage open to make it easier, if you have a Shimano with clutch, turn it off. Shifting to the smalest cog, also makes it easier when re-installing the wheel.
As to removing the chain, why do you want to do this? If it's for cleaning not really necessary, can easily do a good clean on the bike with a tooth brush. Also, what speed is your drivetrain? If it's anything over 10spd, a lot of the quick links aren't sposed to be re-used, but you can once you keep a spare, you will need quick link pliers to get them undone. If you're running 10spd, KMC make reusable quick links that undo by hand.
Best advice I can give is to head to the Park Tool Youtube channel and check out their repair and maintenance videos, then search YT if you want more info, loads of stuff out there to watch and learn.