From experience on Korean Server They do have Advanced classes that you can choose between 3 of them. There is a Talent Tree you can build but when you advance up choosing between 1 of 3 advanced classes you will only get 3 new skills.
Each of the 5 classes has 3 trees they can expand into. You start out at 0 Stars for that class. As you gain MASSIVE exp you gain star levels. Star levels grant permanent stat increases and temporary skills/permanent skill.
At Star level 1 and Star level 3, you unlock a skill for that spec/role. This skill is available as long as you stay on that advanced class.
At star level 5, you unlock an upgrade to one of your skills in your current kit. This skill is permanent and is always available no matter what advanced class you gain.
Yes, you can swap Advanced classes. You will need to gain increasingly more experience every advanced class you go in, making it more and more challenging to level.
Due to the XP required to be gained (in KR, switching also required XP, 900k i believe, don't know if ours will be the same), it is why i wont be using my Norden's Favor until these are unlocked. These will not be available at first and will be unlocked once the Devs deem it fitting to do so. Getting to 50 is easy, building the branches of a class is the most time consuming. Long story short, I'd recommend those who get Norden's Favor (by whatever means they are gotten), save them until this system is unlocked.