Is it different from, for example, litecoin?
Yes.
But why? Because they have different genesis blocks and seed-nodes, they will not be confused in any way.
To make sure that there's no crosstalk or confusion in the first place as figuring out that they have different genesis blocks still costs bandwidth and computing power.
And are these values arbitrary? Or are there any rules for choosing them?
They're arbitrary. The common recommendation for new altcoins is to just randomly generate new magic bytes.