Typed a long post but got error due to 30 minutes limitation. This is a rewritten post.
The legendary shifter is limited to basic beast and magical beast form, unavailable to elemental nor plant. So while you can get an ability that allows you to do chimeric animal aspects, you cannot combine beast shape with either elemental nor plant. Meanwhile, feral shifter the druid archetype isn't limited by such.
Elemental nexus feels like a kinetic stuck with elemental fist with less tricks but elemental body.
The intro about the book is a bit misleading. You cannot really play a chimeric elemental because expanded elemental replaced chimeric aspect, and from the wording it seems there are only the base 4 elemental available. You're also forbidden from taking a feat to learn basic animal shapes.
You only beat the druid in elemental form I progression by one level, later the elemental nexus has the same elemental shape progression as the druid while missing many shapes.
For example, elemental nexus learns 3 type of the basic 4 elemental, while vanilla druid has it all (animal, 4 elemental, vermin, verdant, shapechange) and only get better with archetypes.
Oddly, it has one line claiming you cannot gain magical beast form. <An elemental nexus cannot take the shape of a magical beast.> But there are no way gaining magical beast form from the book anyway unless by heavily multiclassing.
Dragon archetype is stuck with one scale color till mid level. It's also a bit weak, highest buff he can get before level 8 is +2 to STR & CON and cannot fly in said shape till level 11.
Here, the ability draconic shape also says altered shifter shape, however it does not specify about "cannot take the shape of a magical beast" unlike the elemental nexus.
In later sector of the booklet, bestial root specifies it (draconic shape) could be one of the prerequisite to learn shifter shape (without magical beast form), therefore I believe it's editing errors.
The giant archetype loses the ability to change into any animals other than a giant, unlike a goliath druid who has a limited selections of animals other than giant to choose from.
However from the way it's sentenced I would say you can turn into a gargantuan / colossal animal if you take bestial roots, making it bit more viable.
Overall I would say the book is an improvement over the vanilla ultimate wilderness shifter, but often feels lesser lacking in shape choices than a druid.
There are also oddities such as the prestige class almost nullifies the point of the dragon archetype at the same level.
I think it would be great if the archetypes were combat styles that player get to choose from like ranger rather than replacing most features.
Personally, I found myself having trouble with some of the art direction. Back in the inner sea campaign book, the humans look varied despite they're all humans. In ARG, there are many portraits for different races that somewhat look alike and many of them have the noses (and face) of Gerard (who is supposed to be unattractive) from Dragonlance novel. Otherwise, most none "human-faced" race have good portraits.
Also kind of disappointed in lack of insect people, and felt the book being too short like the Ultimate line.