Loading is a litlle bit long. Because of the way Godot seems to work with Web builds, I have to laod, on the back, all the models and SFX, otherwise, each time a new model or SFX appears on screen for the first time, player experiments a terrible lag.
About the frame rate, I've seen some people streaming it and they didn't experience that issue. Maybe the game is too demanding for your computer's possibility (and, of course, not very well optimised)...