I haven't tried any of these 2, but answering your question if they are the same exchange or not, I've provided references from their Telegram group that may help you understand their connection.

To summarize the details from the images and links provided below:
   1. OkCoin and Okex are different companies, but all accounts are integrated (meaning you can log in on both sites using the same log in credentials)
   2. OkCoin is for Fiat to Token pairs, Okex is only for Token/Coin to Token/Coin pairs
   3. OkCoin is fully regulated and compliant to US Laws, it follows all regulations of every Jurisdiction



https://t.me/okcoin_en/309 , https://t.me/okcoin_en/310


https://t.me/okcoin_en/342 , https://t.me/okcoin_en/343 , https://t.me/okcoin_en/344


https://t.me/okcoin_en/1324 , https://t.me/okcoin_en/1325


https://t.me/okcoin_en/4258


https://t.me/okcoin_en/5489


https://t.me/okcoin_en/5493 , https://t.me/okcoin_en/5494


https://t.me/okcoin_en/7486 , https://t.me/okcoin_en/7487