Can I use Migration Assistant to copy data from 2 different Mac computers to my new Mac?

I have some additional thoughts to offer. After using Migration Assistant to copy the first computer's data to the new one, only copy files from the second one, plus any additional apps which are not on the first one being copied. When copying the second computer do not copy the person data and preferences.

Yes, but:

Migration Assistant wants to copy entire Accounts. Copying from two sources will give you two accounts, plus any you have already created.

Migration Assistant does not seem to understand 'Merge'.

You are welcome. Enjoy your Mac.