Does extending a disk decrease performance?

[Ekko]

I just bought a 3TB Seagate Internal HDD and after I checked it on Disk Management, I found out that it was split into 2.2TB and 756GB. After researching, I learned that my HDD is MBR by default and can only contain 2.2TB at max. 

I was fine with it since I thought I could just use the 2.2TB and 746GB so I partitioned my 2.2TB to 5 partitions:
1. 200GB - OS (I made it into 200GB since I'll transfer it onto an ssd after I save up to buy a 250GB Samsung 850 Evo)
2. 500GB - My Files
3. 500GB - Games
4. 500GB - Song & Music
5. 347GB - Development Programs

And when I right clicked the 746GB to create a simple volume (for my 2 brothers to dump their files into since they sometimes borrow my pc), all of its options are greyed out aside from the properties and help.

So what I did was searched a bit and found seagate's software that can extend the 746GB so I may use it. Now my question is, will this 746GB perform slower even by a tiny bit? Or will it function the same as my 2.2TB?

[Godlygamer23]

It's all on the same drive, so if you are writing data to one partition, another partition will be directly affected as the drive is busy working on the first partition.