I'll start since this year I'm finally in the process of building my first startup, even if it isn't official yet.
What is your tech stack?
I use React with the Remix lib/framework together with Mapbox for mapping purposes and PostgreSQL and SQLite for data storage. I host everything on a GleSYS server. I also use some C# that acts as a plugin to retrieve and sync data to the web app.
Why did you choose it?
I chose it because I am building a thick front end application and because it is tech I already knew. I need a lot of client side functionality so using what tech I already have knowledge of seemed easiest and I can bring whatever I learn to my day job and vice versa to get the synergy effects.
Do you think your choices had any impact on your success or failure?
Haven't had failure or success yet since I am still in the process of building it.