Having studied the book, you have some idea of what each Tarokka result can entail, and you can let this "foreknowledge" inform Madam Eva's reactions to the cards as they appear. If you draw
the 7 of Coins, you can hint that the location of the treasure isn't very far away; if you draw the 9 of Coins, Madam Eva might shake her head despondently and say "Maybe save this one for last."
It's easy to want to add merely emotional clues, to add color without giving too much away: "It is in a place of dread;" "I feel the presence of mournful spirits near this item;" "This place is cold and silent." But there's so little emotional contrast in Barovia that sentences like these can easily fade into the background noise of doom and gloom. Specific information will make your players' ears perk up, and if your goal is to create a memorable experience, you can afford to drop a few extra hints.
For example: Many of the speeches for cards that clue
locations in Castle Ravenloft don't actually refer to the castle ("We know it's in a crypt. Do we know where a crypt is?"), but Eva can add something about "beneath the Devil's tower" or glance nervously in its direction.
If the players feel like gabbing it up with Madam Eva about each card, trying to pry hints out of her, go ahead and respond according to the character you've built in your performance—but to add emotional texture to the scene, make her insist on total silence before she turns over the next card.
The use of a real deck is so effective because everyone loves props. The description of Madam Eva's tent provides a lot of inspiration for additional props: Mysterious lights, a crystal ball, and a black velvet cloth. I think this cloth is a good thing to focus on because you can slowly unroll it before you lay the cards down, which is a very evocative and almost ritualistic action. Even if your players forget what cards you drew, they will remember the appearance of that cloth unrolling across the table.
If you can't get a piece of black velvet, use whatever spooky-looking fabric you can get your hands on, and then change the words "black velvet" to whatever you're using when you read the description, so that the players will think you are following the details in the book exactly.
(On the subject of
Strahd's Enemy: Some of the results are more interesting than others. The book gives you the choice between NPC A and NPC B for some results, apparently according to what kind of Challenge Rating you want for the party's ally. Obviously you want to figure out your choices in this regard ahead of time. But for my purposes, I didn't really want my players to end up with either version of the Broken One, the Horseman, or the Innocent, so I just removed those cards from the deck. If you're not comfortable with the full range of randomness in the book, you can create "massaged randomness" without the players finding out.)
Only if it's not celestial.
The rules on Find Steed and Turn the faithless are clear, you don't get to choose which fey or fiends are turned when you Channel Divinity, but you can choose to summon a celestial as the mount, so do that in order to avoid friendly-turning.
Best Answer
The "Alterations to Magic" section on page 24 of the Curse of Strahd adventure mostly describes how teleportation and planar travel are affected by the Barovia demiplane. The "Cosmetic Spell Modifications" section, which is the part your question refers to, states (emphasis mine):
In other words, the spell modifications listed are just some examples for optional rules, not RAW that you must abide to, and a DM running this adventure is free to use all, some or none of these suggestions in addition to any number of other cosmetic modifications they care to make.
This means that find greater steed may be affected in this way if the DM chooses to do so, but even find steed doesn't have to be affected at all in the first place. It's all up to the DM.
It's also worth noting that find greater steed was released in Xanathar's Guide to Everything, which came out after Curse of Strahd, so there'd have been no way to include it in Curse of Strahd anyway.
Furthermore, even if the spell did exist before, it's a 4th-level spell, only available to 13th level paladins or 10th level bards, and given that the adventure only goes up to level 10, the designers may have chosen to leave it out as it would be unlikely to come up anyway, especially considering that they had already included find steed, which is already an adequate example to guide the DM on how to cosmetically modify such spells (and again, the spells listed are only examples and suggestions, not an exclusive list).