I have a pantheon! The balance of ten elements is the main focus of the fantasy world they oversee, so they represent one each!
1. Do mortals know that the deities exist? Is it obvious that the deities exist or is it a faith-based belief?
The mortals in this world are actually molded in the shape of each deity (i.e. there are ten elemental races too), and there are historical records of the deities existing. Even beyond that, the mortals' own cultural mythologies line up in ways that show such a connection--every culture has a single patron deity, stories about that deity interacting with the other deities, etc.
The deities were the early leaders of their people, intending to show the mortals the way of the land, and then giving it over to them to carve their own destiny. HOWEVER, a great world-spanning war took place in the classical era, partially starting because of miscommunication between mortal leaders that slandered the gods' names, provoking other mortals to war. Because of this hubris, the deities vanished from the world, stating that if the mortals wanted to cause their own war born of arrogance, they shouldn't be dragged into it. This was before photography, so old art and stories of the deities are all the mortals have to go off of nowadays.
The deities are still out there, but don't directly reveal themselves to mortals anymore. Because of this apparent radio silence, some modern-day mortals believe that they were just myth.
2. In what type of light (positive, negative, neutral) do mortals and the deities see each other in? Does this affect any myths or legends about deities or any events that the deities cause?
The deities in Rixile are unambiguously a force of good (as there are other things in Rixile that represent evil). But since they're closely intertwined with their own mortal race, and also several mortal nations, everyone's got a bunch of opinions about everyone else anyway. Some myths get skewed based on a culture's opinion of a deity or its people...Ignus (god of war) and Nocturne (god of thieves) are especially unpopular...and they're allies! There are plenty of stories about deities annoying each other, too. Nocturne/Sonata, Mist/Terra, and Aether/Galvan are all famous rival deities due to various aspects of their own that just happen to be fundamentally incompatible with the other.
3. If there are more than a few deities, which deities tend to be the most liked or disliked by mortals and why? How unusual is it for someone to like a commonly disliked deity or dislike a commonly liked deity?
As stated above I think Ignus and Nocturne are the most unpopular. Ignus is the god of war (amongst other things), and his people had a wide-spanning empire and are known for being colonialists. Nocturne is his ally, and his people are known for being particularly good spies. Despite this, the deities are always expected to be prayed to regarding their specific domains; Ignus is the god anyone in a war is praying to for victory, not just his own people! His people are just the ones that reflect his main element, fire. Since there's a wide variety of races and cultures, each culture is going to have a different opinion about the whole pantheon...Nocturne's own people love him, for example, and hate Sonata, his rival. So I wouldn't call it super unusual, just that people are going to have their biases based on the cultures they grew up in.
4. What types of alignments are the deities? (eg lawful neutral, neutral good, chaotic evil, etc)
Despite their various petty squabbles, the deities are always a force of good, and keep the planet's balance of elements in check. It's just that some of them are a bit more on the chaotic side and others are a bit more on the orderly side...
There are demons too, but they don't count as deities. But that's where the forces of evil come in.
5. What types of deities are they? Are they like abstract nature spirit type deities or are they like tangible ones (like in greek/egyptian mythology) or are they like eldritch abominations or are they something else?
Kinda...half spirit, half tangible? They're technically made entirely out of elemental power, but they can take a physical form. What that form is can even change! Sometimes it's their "preferred" appearance, sometimes it's a mortal disguise, sometimes it's a beast! This further adds confusion to mortals wondering if the deities really existed or not--ancient art of the gods can be of any of their various forms, making it ambigous.
6. Are there any commonly-believed myths about the deities that are simply not true at all?
I think the biggest one I can think of is the concept of a god "dying"; during the great war I mentioned above, some of the myths about it report that some of the gods perished in it (usually who specifically depends on that whole cultural bias thing I mentioned earlier...). I like to think a god can "die," but the dying involves elemental balance going out of whack as the god slowly reincarnates. As the deity is an expression of the element in the world, they can't really die unless that element itself is completely eradicated, which isn't really possible, so they'll regenerate. But since the mortals can't consult the dieties anymore, they're free to interpret a deity's "death" how they will, sometimes using it to taunt members of another race. I know I've already bullied Nocturne a bit, but he gets this treatment a lot, some cultures considering him Dead For Real even though he isn't.