APA muzzle brakes ie fat and little bast@rd are some of the best I've EVER used
Yes, they will come with the +2 Rifle length gas tube.
Barrel manufacturers do not provide guarantees on accuracy because it is not all based on the barrel. Accuracy is based on the barrel, action, trigger and the installation of putting these all together. These barrels are known to provide sub MOA accuracy easily when the entire platform is properly trued and put together.
This barrel should work with the Stag 10 upper. The Proof barrels have a DPMS barrel extension and it appears that is listed on Stag's website. Confirming that with the AR upper company would also be a good secondary way to ensure it will work.
All Proof Research barrels come with one dimple on the bottom of the barrel to assist in proper alignment of the gas block.
The Proof Research PR10 Carbon Fiber CamGas 6.5CM Deepfeed Rifle Barrel will work with the Aero M5E1 and I would use the gas tube that is provided.
This Proof Research PR10 Carbon Fiber CamGas 6.5CM Deepfeed Rifle Barrel should work just fine with the Aero upper. There shouldn't be an issue with the Atlas Barrel Nut but I would contact Aero Precision to confirm.
I would recommend the Superlative Arms Adjustable Bleed Off Gas Block. You can find it here:
https://www.opticsplanet.com/superlative-arms-adjustable-bleed-off-gas-block.html?_iv_code=4RX-RGB-SA0914-SABO-DI-875SM
No, this will not come with a gas block.
No, this is an AR platform rifle barrel. the RPR is a modular, chassis based rifle system.