for the first boss you should avoid worries about materials from other seeds.
it is the same difficulty and merely wastes your energy with the game and distracts from the game experience for beginners.

building in valheim allows you to preserve the look of an area without stripping it bare for materials. then another seed can preserve your aesthetic standard as a second source. it is more relevant in multiplayer building.

the second boss presents more variables and you will see more choices where resource logistics arise as you go further.

in the game you are presented with the choice of which character to use and then which world to play upon. you require two worlds and then go back and forth between them with pockets full...or empty.