dellboy__ :
Using the motherboard port will I get the same speeds as using a PCIe Expansion Card?
I have read that some onboard m.2 ports only run at sata III speed, and using a PCIe card ill get the most out of the m.2 drive
You read wrong.
That depends 100% on the actual board.
Most boards with a m.2 port will run at normal PCIe speed.
Some few may limit it to SATA III.
What does yours do? What does it say in the user manual?
Specifically, it says this about that m.2 port: "32Gb/s M.2 X4 support"
https://www.asus.com/us/Motherboards/X99-A-II/