Elemental Savant is from Complete Arcane. Their tenth level capstone power Elemental Perfection reads:
At 10th level, an elemental savant, through long association with elemental entities and extensive study of their secrets, completely transcends her mortal
form to become an elemental creature. Her type changes to elemental. She no longer needs to eat, sleep, or breathe (though she must still rest to regain spells). She gains an elemental creature’s immunity to stunning, and she is no longer subject to extra damage from critical hits or ﬂanking. An elemental
savant gains the speed and movement modes, natural attacks,
special attacks, and special qualities of a Medium elemental of the type appropriate to her elemental specialty, as noted in the
Monster Manual, except that the save DC against her elemental attack form, if any (whirlwind, burn, or vortex) is 20 + her Con modiﬁer.
Upon achieving this state, an elemental savant’s appearance
undergoes a minor physical change, usually to the skin or eyes. An earth elemental savant, for example, might acquire gemlike eyes and hard, pebbly skin. Anyone who shares the
elemental savant’s predilection for study of her chosen plane
immediately recognizes her transcendent nature. She gains a +2 circumstance bonus on all Charisma-based skill and ability checks when interacting with creatures that share her
elemental subtype (air, earth, ﬁre, or water) and with other elemental savants who have chosen her element.
This means at tenth level you get these traits - nothing more. Note you don't "acquire these traits at will," they are always in effect. So yes, if you are an Air elemental shaman you can fly 100 ft., perfect. The description in the second paragraph seems pretty clear that you're not now 100% made of that element or anything - though even if you are it doesn't matter, see below.
The class also says if you're going outside the standard elements, the GM will need to figure out some of what that will mean. If an Electricity Elemental can pass through metal, then you can - if that's not a defined power (meaning something explicitly listed speed and movement modes, natural attacks, special attacks, and special qualities) they have, then not. Note that by the rules an air elemental can't pass through a chain link fence even though "they're air," it's not one of their RAW powers. Your GM may vary that based on their vision of how the world works. But you are not entitled to anything as e.g. an air elemental savant other than fly, whirlwind, air mastery, darkvision, and elemental traits (most notably: Immunity to poison, sleep effects, paralysis, and stunning, Not subject to critical hits or flanking, Elementals do not eat, sleep, or breathe.) That doesn't say gaseous form, that doesn't say immune to physical attacks, it doesn't say anything else.