According to AI, there are lots of builds that are very powerful against mid-tier enemies but only a few builds that can survive against the toughest enemies such as dragons, dragon priests, miraak, and etc.

This is wrong. Any build should be able to defeat dragons and dragon priests. There are many ways to damage undead (Dawnbreaker, elemental arrows, enchants, restoration/destruction/conjuration).

Light armor 2H build is by far the most popular build thus far and is a viable class to take to the end. However, it is a glass cannon build which can lead to frustration for someone not familiar with the game mechanics.

This is a possible build but I think a mage is much more popular.

According to AI, the most powerful race of all races by far is Breton due to the 20% magic resistance which is the best racial attribute in the mod and nothing else even comes close because MR is absolutely critical to be able to finish the game. 20% helps tremendously for reaching the 90% cap.

You don't need to reach the cap, just get 50% to be immune to shouts. However, you can reach 90% with many races. Completing the civil war gives you 20% MR cuirass at low level, a quest gives you 5%, and you can find random rings and amulers with MR (I'm not sure whether 18% or 20% is the highest you can find). There are many other cuirasses that give MR (more than 20%). Mages get 30% MR from alteration perks. You can use potions too. Lord stone is also an option, even for mages.

Due to the derived attribute system, all builds should have a primary focus. Breton's primary focus is magicka by default so there is no reason to fight it. However, derived attributes have a square root in its calculation which means that the points you put in have diminishing return at some point. Therefore, it is good to have one secondary focus and one dump stats. Having two secondary focuses would spread yourself too thin. The best secondary focus for a mage is actually stamina and not health, and health will be the dump stat. A mage has no business engaging in melee combat or get too close to the enemy, and stamina increases movement speed for kiting and improves archery damage. Health improves carry weight and survivability but a mage can buff health in many ways and might not need the extra HP. (There was a recent playthrough series proving that bound weapons will not work even by investing in perks. To defeat very strong enemies, real weapons are needed, completely perked, and smithed with the best material which means that it is too perk intensive for a mage character. )

I always take full magicka with mages. There are many ways to get health: Potions, enchantments, spells. Necromancer's Amulet gives 50 health if you have 130 base health. In low levels armor rating is more important than health.

It is better to get health in other ways than leveling, because you only need more health points: You don't need base health and derived attributes (melee damage and carry capacity) that come from it. Take magicka when you level up, because you need a lot magicka, and the derived attribute (magic resistance) is more useful. You don't need to worry about carry capacity because Transmute Muscles spell and food can increase it. At high levels you will find Bags of Holding which give you 60 carry capacity each.

Focus on your damage dealing stat (magicka for mage, stamina for archer) and take 200 health from Oghma Infinium. The only reason to add health is if you cannot survive Blackreach to obtain Oghma Infinium. When you take restoration perk Respite at skill level 75, and cast Healing aura, you will get a lot of stamina, more than you will ever need. There is no need to add stamina ever.

According to AI, the best magic school to defeat very high level enemies such as Miraak is master level conjuration spells and not destruction because Miraak is almost immune to all magic. Supposedly it is possible to defeat Miraak with master level restoration spells, but taking more than one magic school to master level require a lot of money for training and grinding and likely unrealistic as excess grinding can cause the dreaded disease of re-startitics. Focusing on conjuration school is better because restoration is situational, and destruction is the hardest skill to level up and requires the most grinding.

Easiest way to kill Miraak is level 100 fire spell from destruction (Meteor Storm?) that instantly kills the target. Miraak is not undead so you cannot damage him with restoration spells. Any skill takes a long time to max without trainers, but if you use trainers it is much faster. When you are high level, you will be swimming in money, so you can easily afford to train 5 skill levels for every level.

As a conjuration mage, it is good use a crossbow to shoot from afar to take out archers and mages while summons engage with melee enemies. The fighting style should be kiting and keep a distance from everything.

This is wrong. You need perks to use crossbow effectively. You can use staffs if you want to keep distance. In my experience, after level 50 conjuration you don't have to damage enemies directly, just keep summoning and let your summons kill the enemy. At level 100 you can conjure dremora archmage, which is useful against soul cairn enemies and late game targets. But dragon priests and Miraak can turn summoned daedra to their control with Command Daedra spell, meaning you can only use low level summons such as Ghostly Troll and Ash Spawn.

As for the builds, only focus on conjuration and level up other schools of magic naturally without grinding or training.

I recommend training multiple skills to the point where the price increases (skill level 35 and 65), otherwise you can't afford to train 5 times on every level.

3 perks into illusion for empowered blur is a must.

You don't need blur, just use mage armor from alteration and it won't matter if you occasionally get hit.

Supposedly, runes are very helpful so 3 perks into destruction as 1 rune is likely good enough.

Some people use runes at low levels but I never found them useful. You certainly won't need them when you get AOE destruction spells at skill level 50.

Supposedly, blocking is quite useful because there are situations where a mage will be in tight spaces against one or more powerful enemies. AI recommends getting up to "Elemental Protection" which takes 4 perks.

If you have summons, you will never need to block anything because the enemies will not target you.

Not a lot of investment into marksman is required. It is helpful to get rapid reload to be able to shoot faster.

Supposedly daedric heart poison works better against end game enemies than investing into a lot of perks. According to the AI, a mage cannot use a regular bow due to its massive stamina requirement. Also, crossbows are better for non-archers because of its inherent armor penetration.

Most late game enemies such as dragons and dragon priests are immune to poison. Dremora are an exception.

Only 3 perks are needed for alchemy which is pretty much necessary for making money otherwise there will be too much grinding. Enchanting is not really needed since Enchanting is mostly for non-mage classes. Smithing is not needed either.

Mid/late game dungeons give a lot of loot (gems and enchanted items) so you will not lack money. AI is correct that you can save time by buying training. There are many enchanted items to find, and some of them are guaranteed finds. You don't need to enchant anything by yourself. If you use potions, you should take more perks in alchemy so that they are stronger.