TBH, it sounds like they are using the triple class from THJ, and going for a harder difficulty.
The casual dad server is going to remain the untapped approach in all of this. You could solo everything in THJ with the right class combo's, and duo everything no matter what you picked.
You can leave the dificulty set to 0 if you want to just stroll around I'd imagine.
In the discord the dev Ailia was answering questions the other day, some of these might already be in the FAQ.
Things like research & poison making are gone and there's a new poison system,
every class vendor sells all spells for the class,
2H is the most popular style in testing with dual wield 2nd,
some class self-only buffs are permanent (yaulp/frenzy),
cleric has the most new spells of any class,
aa's are autogranted for some things like innate crit,
arrows/throwing weapons aren't stackable,
all armor & weapons that are equipable are upgradable even player crafted ones except stackable/no-rent items,
you get aa xp and normal xp both at 100% all of the time and there are custom aa's.
DT removed from the 3 planar fights, their mechanics tweaked
Alternate ways to upgrade items to help with last few ranks to +10 your equipment
Upgrading gear reduces weight
Map is in among other QoL features
I never played THJ so can't say how much of this is same/different.