I used to post my story on RoyalRoad a while back. The experience was nice. You get a ton of views soon, though the readers are very silent and rarely interact. I didn’t get far enough myself to see if it is true, but almost everyone there told me you won’t get a good following before you have a good chapter count and a consistent record of uploads.
The forums seem professional, but that is because of the review swaps that go on there like sub for subs go on over here. The review swaps can become a hassle, people are good and are very helpful with review swaps, I have learned a lot from those personally. But there are also a few that will just insult your work for no reason, and encountering them when you are starting will be very problematic. They are rare but are there.
Your performance on RoyalRoad will highly depend on your genres. Fantasy, action, thriller, and stories in similar genres do very well. Romance or slice of life dies out super quick in my experience. The chapter lengths also play a part. My chapters are short and made for Tapas, they got a good number of complaints.
Overall, RoyalRoad is a good place with friendly people, but uptight, I’ll say. If you think your story can fit, go for it.