That is another good question, SouljaFlight. It's always good to make sure you know exactly what you're doing before taking any steps. This article explains more about how iCloud Photos works, including what happens when it's turned off: Get help with iCloud Photos. Please check the "How do I remove all iCloud Photos content from iCloud and my devices?" section for specific information on the next steps.
To summarize: If you have the full versions of the photos on your iPhone or other device, nothing would be removed on it by turning off iCloud, as long as you use the "Download and Keep Originals" option explained in the article. Otherwise, in 30 days once the photos are removed from iCloud, you will not be able to download the full photo from iCloud any longer, so make sure that change is made first.
If you have further questions, please let us know. Take care.