Swimming teacher here.
It depends on lots of things. How deep is the water? Can they stand up? What is their balance like?
Noodles are OK for slightly older children who can lie in a prone position or stand up and have the core strength to keep their legs up.
For my little ones to start off with I use a age appropriate ring and arm bands. This helps with mobility and confidence such as just being able to float and play unaided with feet of the floor. Being confident in the water is a huge tool towards unaided swimming.
Once they can start to travel and lean forward (ie. Kicking feet, paddling with hands then a noodle can be introduced.
IME a two year old with a noodle that can't swim will struggle as there is so much going on trying to get feet off floor, leaning forward, using hands, kicking feet. I'd just focus on her leading to float, travel and play at her age.
It may seem that you are going backwards to add a ring but if you miss out some of the fundamental stages of learning to swim you will end up with issues a bit further down the road.
Things like getting her to lie on her tummy like a crocodile in the bath or pool steps and kicking from the tip toe , blow bubbles, gently putting face in water all goes towards when she is confident to get rid of the ring and go it with the noodle or armbands.
Arm discs are very under rated. You can pile on three ar a time and whittle down to none when she has a good prone position. I would however use full on armbands at first so she feels completly safe.
Costumes with buoyancy aids tend to give support in the wrong place and are a waste off money I think and more of a hindrance.
Good luck