No, I do not work for for Gf/P.C. what is written is all I know.

-the final starter evolutions are not planned to be revealed, however the middle stage evolutions will in the upcoming weeks so you can gauge which ones you'd moreso plan on choosing before the release of Sword/Shield.
-Starter types are Fire, Water-Psychic, and Grass-Rock.
Sword gets a sleek and fast looking Dragon as its Psuedo legendary while Shield gets a Beefy more physical looking Minotaur.
-Eternatus is Dark-Ghost and has it's own Gigantamax form.
-Neither zacian (steel-fighting) or zamazenta (steel-ground) have gigantamax forms.

Gigantamax able Pokémon (that I know of) are:
1. Lapras
2. Gengar
3. Machamp
4. Flygon
5. All 3 Sword/Shield starters
6. Eternatus

About Leon, he wants the become a worldwide famous trainer (one of the most popular and strongest) but once you beat him later in the game, he becomes somewhat furious and embarrassed at the humiliation of not only losing, but losing to a new trainer (the player). He seeks to find the legendary Eternatus to catch and beat you in a rematch with it afterwards but all he manages to do is anger Eternatus causing a surge of dynamaxing across the Galar region with you having to catch the games respective cover legendary in order to stop the chaos Leon has caused.