Timespike
A5E Designer and third-party publisher
I've done some playtesting of the A5e classes as they've come out with various gaming groups I'm in, and I've used existing O5e subclasses with them. It's worked fine.I agree. I've seen some (non-designers) mention taking O5e subclasses with LevelUp classes. Is that even possible? I know they've said that it's "backwards compatible" but I don't think they quite mean it like that. I suspect that it's more that a player could play an O5e character in a LevelUp game, or LevelUp characters could fight the monsters from the O5e monster manual without conversion. But I don't think we can mix-and-match pieces of a character, exactly.
Anyone know?
Here's the list of what I've used:
A5e fighter: Crusader (from Complete Martialist's Dandbook - DM's Guild product.)
A5e druid: Circle of the Branch (from Complete Devout's Handbook - DM's Guild product)
A5e herald: Oath of Battle (from book of the Righteous - Gren Ronin)
I have plans to make a cleric using the Twilight domain from Tasha's and an adept using the Kensei from Xanathar's. The only real compatibility issues I could see coming up with subclasses is if they reference class features that have been eliminated (Action surge or Second Wind, sor example) but otherwise? They work perfectly fine, and I have play experience that says so.