I think the tank chocobo isn't too bad at low levels (the AI was improved recently so it uses its hate moves immediately instead of waiting forever to start), it's just incredibly underpowered at level cap. I have my points spread out between the different skill trees and it makes for a well-rounded chocobo that performs much better than a focused one, you just miss out on the exclusive barding until they allow us to reset points. Arcanist might be rough but I think your level 15 quest gives you Topaz carbuncle which is a very good tank while solo.

For Ecosmith: As you go through the storyline you will eventually have to choose a grand company at level 20 I believe. Since you probably will ask, no it doesn't matter what company you choose, the gear has very little difference between them so pick the one you like best. Once you join a grand company you can get a quest from an officer there that will tell you to purchase a Chocobo issuance with company seals that you get from quests, duty roulette, FATEs, and company leves. After you get the issuance you just take it to the stables NPC for your chocobo.