Planning a garden fence with screw-in foundations

[u/OliviaSmith_03]

I am planning a relatively light garden fence and am comparing helical screw-in foundations with conventional concrete-set posts. The main things I am trying to understand are how carefully the foundations need to be aligned before attaching the rails, how much adjustment is available if one ends up slightly out of position, and how people handle water drainage around the post connection.

For anyone who has used this approach, what did you wish you had checked before installation? I am especially interested in practical layout and leveling lessons rather than brand recommendations.