If they do would it be OK to get quite a tall fake plant for the Q tank where I will be putting the betta, before putting him in a tank with Corries?
Don't bother with live plants in the q tank. If the fish in there gets sick you have to throw them away since they can't be bleached. Bettas don't NEED tall plants, but they do like them to rest on.
Many Betta owners provide a tall plant for their little friends to sleep on because they have to swim to the top to "breathe" through their Labyrinth organ on the top of their heads at night. It saves them having to go so far when they are so sleepy. It is just a courtesy. Use a fake plant in your Q tank absolutely. They will love it just the same and be grateful for your thoughtfulness. It is just an offering of love to a tired little buddy. A lot of the time you will even catch them using it as a resting place during the day. They get quite attached to having their own plant. When you put them into their final home if they have had a tall plant in their quarantine tank, please provide one for them in the new tank even if it is a fake one. In fact the fake one they had would be nice since they are used to it. It will help them adjust.