Hello There,
Can I change between 2 account names without any hassle or wait ?
Hi, do you mean usernames? This can be easily done from the account and there shouldn’t be any wait time. At least that was the situation when I checked username last tine on an account 
Just go to Edit Profile and change it from there.
Yes, IG only allow you to change your IG name twice within 14 days. You can change the other account name without having to wait.