Migrating using ThunderBolt-2

<<. have read that using a TB cable is the most reliable way of doing so. >>

That is ONE point of view.

But you will need a US$50 adapter and a thunderbolt-2 cable at another maybe US$25 to do a one-off transfer that way.

Readers here agree that the best way is from the old Mac's Time machine backup drive. Drag it over to the new Mac and find a way, however slow, to connect it, and let the Migration begin.

the only dragging you do is heaving the physical drive around. The rest is a standard Migration Assistant session, OR, if you have not yet created ANY user accounts on your just out of the box Mac, Setup Assistant.

Setup Assistant is a special case where, at FIRST run, you do NOT create a NEW user account, but tell Setup Assistant to use a Backup disk as the source. "All the 'stuff' is over there, on that previous Mac's Time machine backup disk" now attached to your new Mac.

LexxDataRecSolutions wrote:

Just use a standard Ethernet cable to connect the two Macs. You will achieve a copying speed of about 120 megabytes per second, which allows for copying around 400 GB per hour. However, the actual speed will be lower because copying hundreds of thousands of small files slows down the process.

ThunderBolt-2, used on older Macs, is not plug compatible with ThunderBolt-3. Its use requires a ThunderBolt-3 <-> Thunderbolt-2 adapter, US$50, plus a ThunderBolt-2 cable.

Just use a standard Ethernet cable to connect the two Macs. You will achieve a copying speed of about 120 megabytes per second, which allows for copying around 400 GB per hour. However, the actual speed will be lower because copying hundreds of thousands of small files slows down the process.