the level bp is associated with the level its made in whereas a actor can be placed in any level and have multiple instances. both have different advantages and uses, and also their own complexities. the level bp for example can easily reference actors in the level, where a actor has a bit more trouble. a actor though can be referenced by other bps much easier than a level bp can. generally and this is a bit of opinion, the level bp should only be used for things specific to the level. so if you have say a door and its the only door in the game then put it in the level bp, but if you have many doors in the game then it would be easiest to use a actor so that you can create many copies and reuse the actor throughout the game. i guess its something youll understand more once you have more experience. experiment with how each work and youll learn the intricacies of each.
now as for why your spawn transform is different, id would guess that your variables arent set correctly but then again not alot of information given to work from.