Anything printed in 2024 uses 2024 rules. Anything not reprinted in 2024 but available in 2014 uses 2014 rules. Nothing from different settings (no Dragonlance, no Eberron, no Strixhaven etc), anything that is Faerun or setting agnostic can be used and the 2014 version is used if it was NOT reprinted and changed. It is a really elegant and effective way to mix rules and I have played a bunch of campaigns doing this.
So with these guidlines class is 2024, Gloomstalker, Hunter, Fey Wanderer, Beast, and Winter subclasses are all 2024 and 2014 versions of those are not allowed, also Bladesinger is the 2024 Bladesinger only. Plane Walker, Drake Warden, Swarmkeeper subclasses are all available and are the 2014 version.
The only exception is subclasses that start at level 1 or level 2 in the 2014 rules now start at level 3 and you get the level 1/2 abilities at level 3 instead of 1/2. This matters for Bladesinger but not the Ranger subclasses.
