With RN, I always only use yarn start to start the metro bundler, and go to XCode and go to Product / Perform Action / Run without building. This saves 1-2 minutes of build time that yarn run:ios does.
You should include a normal yarn start script by default (generated by using create-xp-app), to make it more familiar to RN devs switching to RN-XP :)
I guess yarn run rn-cli start is the same, but still..