This is my concern in a nutshell, unless someone has a tool that spits out a properly formatted .htaccess so I can migrate my HTTP headers and redirect rules.

Netlify's playground is easy to use for setting this up, but I'd also like to have this available in a standard format - just as an escape hatch in case I need it.

https://www.htaccessredirect.net is there, but I'm thinking even less configuration if that's possible.