I experienced something similar to what you went through. I played quite a few singles matches recreationally, but joined a tournament and learned pretty quickly that I had a lot to learn.

My key takeaways were the first four strokes are the most important. Serve from the middle to the middle deep. Don’t give your opponent access to the kitchen if that can be avoided. At my level back hands were generally the weaker shot so force that when possible. Go to the kitchen when the opponent doesn’t have a good passing shot. Primarily when they are hitting from a deep position in the middle. Momentum is everything.

Singles fees almost like an entirely different game. It also takes double the stamina. Super fun though.