I started off doing similar with my older son when he was 13 though he was just looking at drawings through art sites and inappropriate comics through a streaming service at that point. We did remove the comic app whose parental controls just weren't working as we all agreed it was too tempting and replaced it with buying and downloading e-version of comics but in general, we had a conversation about how it's natural to be curious, the unrealistic and damage of porn, and put in guidelines but didn't push it further at that point due to how comparatively tame the images, his responsiveness during our conversation, and because of his general personality.
His father and I gave him appropriate sex-ed websites under the idea that his curiosity was natural but he was naturally very awkward discussing it and hadn't seemed to like any of the books we had on the topic and is still a person who generally does not ask personal questions. I did tell him if he broke our guidelines by going around parental controls or any of the others we had, we would have to remove features and would have to go more in-depth in discussing the damage to himself and others of porn. I thought our open communication and clear expectations were enough.
He went from looking at mildly suggestive fanart and 15 rated comics to viewing pornhub while he was meant to be doing his maths work within a few months. He did this in the living room on a laptop in the middle of the day, it took a couple weeks for him to be caught doing that but I was surprised with how brazen that was.
The reason he gave - he googled something and it was there and he felt drawn to keep doing it after the first time. So, we removed temptation - his phone no longer has browser capabilities, he has to do all his work and internet on the main computer attached to the TV so can't be hidden, and we spent several evenings over many weeks reading through resources on the effects of porn on individuals and the porn industry and discussing it together. It was uncomfortable for all of us, but so are the common effects of early and regular porn usage, so are many of the women in the videos if he is watching pornhub which doesn't check its source material for much really. As I said to my son, if you think you're old enough to watch that, you must think you're old enough to know what goes into that. I didn't go into as much detail as I could, keeping to mostly teen resources on it, but I wasn't going to erase the issues for his comfort.
Sure, he might find other ways. He might try to sneak downstairs when I'm sleeping when his father is working (though he tried that once for video games, found out just how light a sleeper I am as he didn't even get the TV on before I'd followed him down, shocked him a bit), he might see it at a friend's house, he might do many things, but just because it's easily available doesn't mean I have to make it easy for him or give him an environment that enables that. I can open conversations and set our home for his betterment.
As for the drawings, I'd put that under the same rules I have against him showing such images to others if I found them outside of the file he has for his papers and art. Sure, it's nice to see that he's worked hard building up a talent, but then the amount of reference images usually looked at to do that well...I'd be trying to find other ways to occupy his artistic work ethic.