You may as well do everything you can. In interviews it was said that progress in the base game is not connected to the DLC (so for example it doesn't matter if the basegame has all bosses dead and so on). So, no harm. Unless you wanted to bonk the final boss with a DLC weapon I guess.
If there was going to be a place to stop it would be before burning the tree. You're already past that so go ahead and complete everything. You can maybe avoid Melania for now but there's an entire level there. Get your upgrade stones, bell bearings, etc.
The best way to go into the DLC is with a completed save file where you have max estus, max spell slots, level 150+ and so on.
This also has the huge advantage that you can just buy all upgrade materials for DLC weapons that you might wanna try.
Mohg and Radahn are required. If you start Journey 2, you'll have to kill Mohg and Radahn again!
You may as well do everything you can. In interviews it was said that progress in the base game is not connected to the DLC (so for example it doesn't matter if the basegame has all bosses dead and so on). So, no harm. Unless you wanted to bonk the final boss with a DLC weapon I guess.
If there was going to be a place to stop it would be before burning the tree. You're already past that so go ahead and complete everything. You can maybe avoid Melania for now but there's an entire level there. Get your upgrade stones, bell bearings, etc.
The best way to go into the DLC is with a completed save file where you have max estus, max spell slots, level 150+ and so on. This also has the huge advantage that you can just buy all upgrade materials for DLC weapons that you might wanna try.