You just have to be careful about setting up the new computer. Don't use Time Machine or Migration Assistant to setup the new computer. That is only when you are replacing and moving all of your data.
Instead, make sure all of your information is in iCloud. Then, when you sign into the new computer, just turn on iCloud.
The problem is that there are some identifiers in your home directory that uniquely identify your account. If you copy your home directory to a new computer, then there are two copies of that same, formerly-unique identifier. That will break some handoff and continuity features, and likely iCloud Keychain. But if you use iCloud, you'll get a new unique identifier.