"The reason I'm not making this web playable despite being built using web technologies is that I'm targeting Steam for this game. Therefore, I need to make sure the game works well when installed as an executable on Mac, Windows, Linux."

If it runs on the web, it should run the same as an executable, otherwise your exporter is broken. I would likely debug on the web first (just to get access to chrome dev tools including the profiler and performance meassurement tools). Is there some way to do comfortable debugging/profiling with the way you export via GemShell?

That should is doing a lot of potentially very painful heavy lifting in your statement.

Yes, but before checking the tools and compilers for bugs, it usually makes sense checking and verifying the own code first in a controlled setting.

I think you have to ask yourself what you're trying to get out of this, strategically. I know it's probably a "forbidden" option, but Unity is really good at hitting all the platforms at the same time and giving you the ability to deeply understand why things might be running like shit.

I'm working with a partner on a steam game and it was the most rational choice we could arrive at. Our goal is to make enough revenue from the this project to justify another one. We seek to make a living doing this.

I struggle with the lack of advocacy for effective tools on this platform. If we are being honest about the overall engineering proposition, the trade of moderate, unknown capitalist exploitation risk for platform targeting stability might actually be worth it if the goal is to get the game into the hands of as many players as possible.

Electron/Tauri/whatever is just the start of the battle. You also have to consider different input, storage, etc., systems if you want to hit targets like Steam Deck - which is a huge deal for visibility these days. The web is a nasty abstraction layer once we start talking about things like Xbox controllers.

Make a web game. This isn’t a web game.