Hmm, you could try using scopebuddy, which comes included with Bazzite. You can include any config options in there if you want, but specifically it supports options for automatically configuring width and height, and you can add more arguments as well. Final command here might look like:

scb --force-grab-cursor %command%

I also use a lot of custom configs, for example I'm tinkering with Wayland atm, but keep a gamescope config I use like this:

SCB_CONF="gamescope.conf" scb %command%

The shorter syntax is really nice, and it's nice to be able to tweak a bunch of global options like PROTON_WAYLAND and PROTON_ENABLE_HDR without having to manage huge commands in Steam.