Oh, I'm just talking about the lineage of the rules systems, there isn't really a good concept of "changing something from 4th to 5th edition" because 5th edition comes from 3.5. 4th is an offshoot really.
It does make some sense to ditch "quest" I think - partly because the spell can be "don't do (x)" and that's not really much of a quest, and partly just for simplicity in rules.
This is the study room in their house, although that's not super clear from the art. That's why it has a map table in the middle and some of them are wearing more casual clothes.
in 5e, Geas is a level 5 spell that compels someone to either do something, or refrain from doing something - the compulsion is in the form of the threat of massive damage for disobedience.
Side Note: If you read any of the 5e official books, they say the temple of Tymora is in the Castle Ward, not the Sea Ward... Despite the temples of Gond and Sune (which the Temple of Tymora sits between) being in the Sea Ward.
The gambling angle is pretty much a Tower of Luck (the temple of Tymora in Waterdeep) orthodoxy. While gambling is somewhat in Tymora's purview, it's not a common focus of her followers, which tends to be more "fortune/fate/karma/adventure" focused. Most Tymora worship is done at small traveller's shrines, hoping for fortune or safety on a journey.
The tower of Luck in Waterdeep is unusual for Tymoran worship, it's the largest temple to Tymora in Faerun (and the only one that's remotely close is in Suzail) - part of the money for such a large institution comes from placing it in the noble quarter of town (the Sea Ward) and... not dissuading nobles that donate huge sums of money in the hope of it "buying" them fortune and luck in the future.
The other part comes from the temple sponsoring and supervising gambling houses in the city - most official gambling establishments have a resident Tymoran priest who blesses the proceedings, and is there to assure punters that the house is running a fair game, and not stacking the deck. There are non-sanctioned gambling houses in the city, and they often offer better returns on bets, but... they don't come with these assurances... so really if you go there you're making a different kind of gamble.
This relationship between the church and "sanctioned gambling establishments" might explain why, our of the extensive list of guilds in the city, there isn't a guild of gamblers or gambling houses.
As for Konsi herself, while she recognizes that gambling represents a form of worship to Tymora, she much more subscribes to the "good karma" theory of fortune and fate. Those who do good deeds will be smiled upon by Lady Luck, and their good deeds will be repaid in kind. She doesn't tend to go in for gambling games too much, because they tend to require a bit more calculation and mathematics than she's comfortable with, and thus her knowledge of these games is a little sub-par for the wishes of the church.
It's a fun religion, they even have a casino floor in the church itself where you can just hang out and play some chill cards.
I'm pretty sure that the rules as intended for this one are that it just affects attacks, I'm afraid. Sage Advice repeatedly argues that the intention of wordings like this is that they don't extend to other effects.
Of course, it's perfectly fine to run your table different to sage advice. There's a lot of stuff in there that I think is rather silly, or bad design.
Were you able to see the whole space, you should be able to see the illusory duplicates fine (they're not "vampires" mechanically), but not the real vampire, so I'm in full agreement there.
It's a common trope in media and fantasy lore, Quite a few tropes of vampires are listed in the flavour text, rather than the statblock, and this is one of them.
...All of this is pretty sketchy though, it's definitely pushing the limits of what these spells or abilities are intended for, and "having your image move around inside you perfectly so nobody notices" would require an extreme level of control that I imagine most, if not all casters wouldn't have.
If we're trying to design an NPC vampire to foil the mirror check, it's probably better to have them use a custom spell or magic item that's explicitly for this purpose than to try and repurpose an existing spell to do it. "This amulet creates an illusory duplicate of you that fills the same space as your body. When you turn invisible, the illusion remains visible and moves in a random direction away from you" for example.
This approach has a lot of advantages I think.
If you let NPCs do it, then PCs can do it.
It doesn't feel like you're creatively abusing the rules to give NPCs an advantage
When the PCs beat the vampire and get the treasure they get a lightbulb moment when they realize what happened
The players get an interesting niche treasure out of it they can come up with clever uses for later.
That's not enough to overcome Konsi's crippling embarrassment :)
although... Razira does have Heroism prepared.