[SOLVED] How do I figure out what USB Header I should buy?

[Ace0nPoint]

I have an Asrock Z270 Killer SLI/ac. Trying to figure out what is the least intrusive USB Header I can buy? Something that will plug into the little pins on my motherboard without blocking off airflow to my GPU by using one of the PCI slots or whatever they're called?

From looking at the manual I found here

https://www.asrock.com/MB/Intel/Z270 Killer SLIac/index.asp

And peering through the tempered glass side panel of my case with a torch, looks like I haaaaaave available :
USB 2.0 Header (USB_1_2)
USB 2.0 Header (USB_5)

Why does one have 4 pins and the other 2 (one of which is being used by my case), have 9 pins? What's the difference there?

What search terms do I plug into ebay or newegg or pccasegear or amazon or 'whatever', to get the least intrusive to my airflow, and cheapest solution I can get for more USB Slots in my case?

What is the most ports I can get out of these slots?

I'd like to use those lower 2 slots, to avoid killing my airflow, if at all possible. =)

I'm also considering unplugging a couple of my front USB ports if I can get more back ports, because having USB stuff plugged in at the front is really messy. =|

Also are there any left field solutions I'm not considering? Like an exterior hub or something?

Appreciate your feedback in advance guys. You're always really wonderful and helpful to the point where I generally won't make a purchase without this community's expert advice, and I really appreciate you. I really do. Cheers. =)

 

[CountMike]

Each row of 4 pins is for one USB header, fith one in double roe is just as a key sou you can't connect it wrong way. The single row one (USB 5)is for only one USB header and it's there for use by coolers for instance so it doesn't use 2 needlessly.
If you don't want to use front ones, you can connect them to the back of case with something like this https://www.amazon.com/JacobsParts-Panel-Bracket-Motherboard-Header/dp/B00LV1ODSW

 

[Ace0nPoint]

riiiiiiiiight. that makes sense pal. Was wondering why one of em had 4 and one of em had 9. Didn't make a lot of sense to me. And cheers pal. I'll buy exactly that. You ripper. =)