For the most part I think it's the same, just you can do the story and hit lv50 now, as well as change classes and use the storage.
For the story, here is a guide, it's in Japanese but you can translate the page with google and it's pretty easy to follow. Your main objective is to get at least 6 of the key emblems from the list there. Then something will happen.
Here is a list and guides for important quests Make sure you do quest 030 at level 10, located at the warehouse NPC to unlock your storage, as well as quest 034 to unlock class changing, this one might be a bit tough right at lvl20, so you can either wait, hire powerful A.I characters, or i could come help kill the thing.
Not sure if trials can unlock the hidden classes, but here is a list with guides for the class quests, you will want to do the quests for your class to unlock some armor and a powerful skill. Note that some of these require you to have Version 2 and 3 installed to unlock.
The guide for subscribing should still be valid, don't think they changed anything with that but feel free to ask if you run into an issue with it.
One more question, I picked a warrior, but I'm debating what weapon to use. Is sword n' board better for soloing? If not, I really like the ax!
I used the 2H sword when i played warrior, you should use what you enjoy for now. You will have a team of AI companions so you don't need to worry about soloing or anything.
As far as skill points go, you will be able to reset later so you don't need to stress over that. But here is a skill simulator (in Japanese) for the future.
Ah, I see! Thanks so much for the skill simulator, I was wondering about that! Can't wait to sink more hours into this game