Yeah, I fall under the “it depends” camp too.
So my personal situation with that is - I started RPing when I was still single. To be honest, despite doing quite a bit of it I can probably count the occasions that I enjoyed it on one hand, most of the time it was unsatisfying at best and downright traumatizing at worst (whether it was with actual creeps/assholes, or with perfectly nice dudes where our interests just didn’t align quite right and it’s no one’s fault). Because of that, it wasn’t very hard for me to decide to temporarily stop RPing when I started dating my partner, since I did feel uncomfortable doing it without telling him. Soon enough I told him about my kink, and while we explored it together, it still wasn’t quite the same as a roleplay with someone who “gets it,” so to speak.
Eventually enough time passed that I was feeling the urge to try RPing online again (the number of times where it was like “oh, this one might have potential!” kept drawing me back lol). So I broached the subject with my partner about that exact question - “does RP count as cheating?” And I do think that might be the most important factor, the way both people feel about it as a couple. It’s like with other boundaries outside of RPing - everyone will have different past experiences, different limits, different definitions of cheating, etc. He and I discussed it at length, like “does THIS feel like it would be too far past the line? what about this?”, and I showed him some examples from past RPs. I’m lucky that he’s supportive and trusting so it wasn’t an issue for us. (And then when I did try RPing again and kept getting similarly disappointed I decided it wasn’t really my thing after all and I don’t really do it anymore lol, it sorta became a moot point)
There are so many factors to consider like… Are you RPing with one person and are developing a deep emotional connection with them? Is the RP utilizing characters in third person, or are you playing yourself? How frequent are the RPs? Are they solely in writing or do they involve voice chat or anything else? These kinds of details could affect what the couple is comfortable doing. My general gauge that I went by (outside of the discussion with my partner) was to ask myself “How do I feel about this right now? Does this feel wrong to me?” instead of solely thinking “Would my partner be upset if he saw this?”
I’d certainly be curious to see other people’s take on this!