I'm assuming that the new game will work the same way as the Silver Tower. If so the game has a rulebook and a scenario book. It has a bunch of tiles and some cards.
There are different quests to go on. Each quest has a set of cards and they are randomized in a specific way so that there is an end room somewhere in the last 3 cards or so.
The players start in the entry chamber and then move into the next room at which point you flip over the top card and put the tile down representing that room.
The Silver Tower game doesn't really follow the GW IP that closely. The Dwarf model is based on the fyreslayer and the Stormcast is a stormcast but the other models are not really GW specific or even anything in AoS. The Tenebrael Shard is, I guess, a dark aelf of some description but as far as I know doesn't appear in the AoS fluff yet.
The Saith Mistweaver is probably a wood aelf or something but again I don't know of any GW like figure but that might be because I don't know the wood elf stuff that well.
The Barbarian chieftain is just a barbarian chieftain.
The Simgarite priest is kind of a generic good guy priest with a dog.
If you subbed in a knight, a barbarian, a thief-assassin, a spell caster, a priest and and a suicidal dwarf you could play the game with any miniatures.
Some of the expansion character cards are more GW specific but the original grouping should get you by for a while.
The bad guys are a little more GW specific but I don't know why you couldn't just replace them with goblins, orcs for the tzaangors, cultists and generic daemons.
Although in the latter case the horrors do split.
It is, of course, GW IP focused but with almost, if any, effort could be played with Frostgrave or any other models you posses.