I'm new to this whole 9mm thing.

Here's what I have so far:

PSA Colt Mag block for AR15 lower

PSA Gen4 8 inch upper

SBPDW brace, sounds like they have a carbine length buffer tube(?)

Thank you for any help!

I had a JP SCS on my 9mm build.  Really nice shooting.  

I would try one of their short stroke scs's if I made another.

What is the weight of your bolt?  Total weight of buffer and bolt should be between 21 and 24 ounces.  I use a 6.5 ounce 9mm buffer with a 14.9 ounce Faxon bolt, standard carbine spring.  Runs like a swiss watch.

SBPDW brace is a carbine length buffer tube.
So any 9mm buffer should work fine for you.

A Macon Armory pistol buffer and standard carbine spring works great. Rudy has been doing these for a long time, and he has it down pretty well.

^^^ This.

Here is (almost) everything you need to know about building/troubleshooting a 9mm AR in one post: "Lots of 9mm AR information"

My 9mm colt pattern AR is mostly Quartercircle 10 parts.  They recommended their adjustable buffer (weight can be changed from 5-11oz) and a sprinco RED spring. This setup has been extremely reliable and I’m very happy with it.  I was tempted to get the JP silent capture spring in 9mm because everybody says it smooths out direct blowback 9mm (I don’t think it’s that bad at all).  
I guy at work shot my 9mm AR and decided he had to have one.   He peiced it together from various manufacturers.  I’m pretty sure he has a foxtrot mikes pistol upper though.  He took it to the range to test fire it and guess what???  Consistent failure to feed.  Now he’s gotta screw around with different springs and buffer combos to try and make it run reliably.  Between ammo being really expensive or unavailable and the fact that this dude is a cheapskate, I’m thinking he won’t bother to ever get his pcc ever running.
Anyways.  Buy once, cry once.  Don’t cheap out on parts.

Toolcraft 9mm bcg

7.3 oz. buffer

.308 carbine length flat wire spring

Ran flawlessly from day one.

I'd recommend trying a standard carbine spring.  .308 recoil springs often cover up other issues that need fixing.

CMT bolt
Standard Carbine spring
Guntec USA AR 9mm 8.2oz Buffer

It's worked great for me with light 115gr reloads and hot 124gr factory ammo thus far.

Blitzkrieg hydraulic buffer and a carbine spring, smoothest shooting 9mm I’ve ever ran

I used an Aero Precision lower with a Sylvan Glock mag block under a Foxtrot Mike upper.  I also used the .308 buffer spring and 6.5 oz buffer recommended by Foxtrot Mike.  Frequent failures to eject and anemic ejections when it did.  Finally gave up wasting money and time to get it to work, and bought a Foxtrot Mike lower.  Works great now.  Would have saved quite a bit of money by going with the matched and tuned upper and lower in the first place.

ETA: works great with factory 115g as well as my own 125g and 147g rounds.  Works great suppressed as well.

5.5 ounce RRA 9mm buffer, NFA spacer and standard spring...........both of mine work great with this set up............

oops, wrong thread.

And the consensus is....there is no consensus

Yup.

I've used 5.5oz to 8.5oz buffers with good results. Used carbine, enhanced carbine and even 308 springs....

All worked fine but a standard cabine spring and 7.5oz buffer(real buffer not solid weight) is my preferred setup when using a 15'ish oz 9mm bolt.

Are any of you using the Taccom?  I've done the typical 8oz solid buffer and springco red spring, but I was never really happy with the recoil impulse.

PCC Adjustable Recoil System AR15-9mm