I have written several articles on migrating your stuff to a new Mac. This article has a couple of helpful ideas on how to do a migration from an old to a new Mac in High Sierra. Among other things, it suggests not migrating directly from one machine to the other. I have done two migrations lately to two Macs. Both times I cloned the original to an external hard drive and migrated from the clone to the new machine using the Migration Assistant software. That worked well. Check out the article, I think it is helpful.