If you have 300+ tasks / notes, I’d look at separating the notes out… I expect there are better note oriented apps.
I used to use todoist but now use TickTick- similar but with some extra features. The non-premium is awful though, you have to sign up for a proper workable product (it is cheaper than todoist)
I really REALLY wish TickTick had a two-way calendar sync with anything. That's the one thing keeping me with Todoist. I think they were talking about implementing it eventually. Did this ever come to fruition?