I'm in a similar-but-different weird place rn.
I have my next "main" project that I've been working on writing for the last several weeks. It's an idea that I had on the back burner for a long time (and generated ideas for over time) that I finally decided that I want to tackle next, So I was super excited to get started on it! But much like your 2nd paragraph, it's like... I'm simultaneously excited to work on it, but the more I push into the first draft of the outline the more questions keep coming up, and trying to answer those pushes me away from wanting to work on it as much xD
Meanwhile i've recently started up a "side" project based on a tabletop RPG campaign I've recently joined and I've been cranking through that like mad. I think the 2 main factors are:
1.) I don't actually have to do much writing for it, as most of the dialogue is already made by the other players- I reword things slightly but it's all already on the table.
2.) I've also let myself be a little faster/sloppy with the art on this one, which still looks pretty good tbh and lets me finish strips a lot more quickly.
But so it's like the "quick and dirty" side project has taken over most of my time because it's like... instant gratification xD As it stands, I'm just gonna keep chipping away at both of them as I'm able to~ The important thing is that both projects are still fun so even though one has an awesome concept but is a drag to work on and the other one is like creative junk food, it all works out in the end @u@;;