Any player who is not signed to a roster can choose any practice squad spot they are offered at that point (typically will be with the team they've been with, but sometimes they will choose a team they feel they have a better shot at making.)
Waivers don't apply to vested vets, but also don't apply to practice squads. A team can't claim a player on waivers and put them on the practice squad, they'd have to go to the active roster.
Also, once signed to a team's practice squad, they can't jump to another team's practice squad, only to the active roster (and I think they have to be held on the active roster for at least three weeks.)