Yes, iPhone 8 does have the OTG support.
Though Apple never mentioned the battery capacity on their website, during our review of the device we found that iPhone 8 does have 1821 mAh Li-Ion battery.
Yes, iPhone 8 does have the stereo speakers.
Though, Apple has not mentioned on their website about the same, but during our extensive review of the device, we have found that iPhone 8 64GB & 256GB variants does have 2GB of LPDDR4 type RAM.
No longer the gold standard, the iPhone 8 is still all the phone you need.