Which Brand build stays most reliable for grouped fights?

Brand's most reliable build is the one that keeps pressure through the full fight. Liandry remains the core, then you add either control with Rylai or more safety if the enemy draft can remove you too quickly.

When should Brand's build really be adapted?

You should adapt Brand's build when he no longer has time to establish pressure. If the enemy team can burst him quickly, break his positioning, or force fights that are too spread out, it is better to move up a control or survival slot than to chase the highest damage ceiling immediately.

Which enchant on Brand when the real issue is mainly surviving the first answer?

Stasis remains the most reliable choice when Brand can cast his spells but risks dying before they really matter. If your main problem is surviving through the enemy's first answer, this enchant gives more value than a purely offensive choice.

Brand Wild Rift Best Build Guide (Patch 7.2a)

Brand does not win fights by deleting a target but by dealing constant damage to the entire enemy team. His build must amplify every damage tick and extend fights to maximize passive spread.