First, regarding your question about the portals: yes, you will always be taken to the same position on the upper platform when entering a portal, regardless of the portal that you use (activated by killing the Clannfear next to whichever portal is currently glowing).This position should be roughly above the entrance to the arena itself.

Regarding the wall and crystal phase: since the wall moves clockwise around the upper platform, I generally destroy the crystals in clockwise fashion (i.e. destroying the initial crystal immediately to the left and then moving left around the platform) as well. However, after the first wall, the second and third walls move progressively faster, so if you are still able to withstand the damage from the Soul Churn effect, it is worth your while to run counterclockwise toward the wall if it spawns too far away for you to catch up to it by running clockwise.

As for fall damage, you will have an immensely easier time with the encounter if you can manage to destroy all three Animus Crystals in one go on the upper platform. I totally understand that this is not trivial, especially on your first time doing the arena on veteran (I was in the same boat as you for a long time). Dps is your friend here. Until you have the dps/survivability to withstand the Soul Churn and destroy the three crystals in one go, I would recommend destroying two of the crystals before dropping down. That way, on your second time up on the platform, the Soul Churn damage is reset and you can easily destroy the remaining crystal. If you are a magicka class, your best bet would be to spam shields when you need to drop down off of the platform and then grab the shield sigil to deal with the Crematorial Guard. I can't really speak to stamina classes that well because they aren't my forté in ESO, but if you are stamina, I would simply memorize the position of the Shield Sigil relative to the entrance of the arena (and thereby relative to your position on the upper platform) and grab it as soon as possible upon leaving the upper platform. It is not essential to drop down right on top of it.

Also, I feel your pain regarding the ghosts. I couldn't tell you how many times I would die for seemingly no reason, only for the recap screen to tell me that I had died by walking into a ghost (that I couldn't even see). My best advice on that front is to avoid the edges of the arena as much as possible, since ghosts can and will spawn right on top of you (which resulted in many of my aforementioned deaths).

Beating Voriak Solkyn on veteran difficulty for the first time feels great, and it is certainly an accomplishment, as it is by no means an easy encounter to learn. There are many mechanics to be aware of, and when learning, making what seem like even trivial mistakes can result in a death. But with each death, you learn something new, and you are better equipped for your next attempt. As you said, Voriak Solkyn (and the whole of vMA in general) is very much a challenge of situational awareness.

With all that being said, I hope I was able to answer your questions to a satisfactory degree; if not, I'd be glad to answer any more questions that you may have. Good luck, you can do it!

Just a tip for first clears:

While on top the wall will move faster depending on how many crystal you already destroyed so far.

DO NOT break crystals, bring them all to 10% or so one by one (easier/slower shield when he tries to knock you back down.

After weakening them all you can quickly dispose of em if soul churn is not eating u alive or you can jump down then back up again (in the latter case you can smash a crystal before going back down)

The first shield after a "teleport upstairs" will ALWAYS be slow regardless of how many crystal destroyed so:

Weak them all= shield still slow
Whack one= Shield will get faster but here you can jump down if needed
go back up again= shield will be slow ONCE then depending on destroyed crystals (but u have 2 almost-destroyed crystals now so u can just end them once and for good with little effort).

As for the issue with the portals it's better if you "tank" the CG near the active pad, the clanfear is probably gonna be killed by your AoEs

As for fall damage when jumping off of the platform I had an "Ah ha!" moment when I watched a video and saw the player jump off into the lava. I've been jumping off on the lava side ever since and seem to take a lot less damage.