AnonymUser
Here’s a suggestion, change the way you write the names of the dragon, it can get hard to understand at times. Stick with the True and Noble parts, then add the main descriptor, here’s an example: True Noble Apocalypse Dragon (Radioactive Elementshifting Volcano) You can more easily show the changes between the evolutions like this, while also showing the important distinction of “True Dragon”.
1 and 4 seem to be the options with the best synergy. I feel like his goal is to be the embodiment of every natural disaster so option 4 will provide thunderstorm affinity which can lead to controlling hurricanes and tornadoes. I can also see synergy with the abilities of the winter dragon to cause blizzards and also causing radioactive storms. The metal affinity will also help him in recreating manmade weaponry. Option 1 seems necessary to fuel his future abilities as I can imagine recreating these natural disasters will require a large amount of mana and likely require multiple spells at once to be cast. The magic crystals providing magical defense also can help currently with how long distance spells are used so much against him.
The last option to me seems the best as the metal affinity might just allow him to pull those metals up from the earth, which would in turn aid his hoard/empire as mining can be inefficent, so if he could just pull the metals up to a point, then have them mined, that would be a much better option. Better mana control and all would also be good, but I think finishing the hoard armor would be more beneficial for this evoloution.
100% should be overlord and metal. Overlord gives him better ability to keep an eye on his property when he leaves, and provides him a teleport lifesaver. Metal improves his affinities by fusing to thunderstorm and evolving the metal - it'll also help him with his gold hoard armour, as his affinity will let him control it better. (Also his dragon desires will insist he gets metal control to grow his hoard, and domain control to keep it safe.)
I think definitely the Magic one, and probably the metal one. With the magic ability to grow mana crystals, combined with the ability to grow (fake) metal, he can probably combine them to form some steel crystal alloy which will be really good defence against magic & physical attacks. With the domain being the main racial ability of a dragon It would make sense if he had the option to get the overlord secondary domain in a future evolution
options 1 and 4 are likely the best pick the elemental transformation is cool and all but way to much of a glaring weakness. where as with 4 he can make all those metal rails/projectiles for his railgun spell making it so much more effective not to mention just imagine millions of floating elemental metal as weapons to just use when ever he wants.