Considering the WAY crazier age gaps in my own story (the biggest romance plot in one of them had a 26 yo and a 77 yo couple) It's generally not an issue as long as they're both adults.
Here's my new story.
https://www.scribblehub.com/series/466382/free-lances/
Would appreciate if you could also post the review on RR as well. I'm currently on Rising Stars there.
Done in the classic style. If you're tired of all the LitRPG/Xianxia/Harem/Smut around, give Blood Demon's Retirement a look. Maybe you'll enjoy it. ;)
Royal road has a hard limit that no more than 15% of your chapters should have explicit content. But otherwise doesn't seem to limit the explicit part.
I've definitely seen several stories with explicit stuff do well there. Everybody loves Large Chests and Blue Core comes to mind.