Arduino nano, Unexpected behaviour

Hello there.

My Setup Computer, OS, etc
HW - HP envy laptop, 32GB ram, Targus expansion controller
OS - Windows 10 Pro
This is my development machine for html, css, javascript, C++, C#(my apologies, client requested, forgive me).
And of course Arduino dev, IDE 1.8.10, AVR boards 1.6.23, MegaAVR 1.8.4
Nanos sourced from Amazon, MC marked as "MEGA328P".

I had one heck of a time getting programs uploaded to the nano after having no issues at all with the Uno or Mega 2650.

To make the Nano work I had to select "ATMega328P (Old Bootloader)" from Tools,Processor.

Also strange is that the same physical Com port changes names(COM5 -> COM6) going from Uno to Nano.

I'm not complaining as uploading work anyway. Just Seems unusual.

In the beginning of 2018, Arduino started shipping Nanos with a new bootloader. One needed to get the (then latest) IDE to be able to program them. That also introduced the 'old bootloader option' so users of the older Nanos still could program them.

Clone manufacturers will probably for the rest of their lives stay with old bootloader so will nore than likely always need the 'old bootloader option'

It's very normal that com ports change between boards and between USB ports on the PC.