Thanks for the response Rick.
I have been looking into this myself since posting here and have started to get closer to a solution I believe.
I looked back at previous projects to see if similar had happened and compared settings within these Hype projects.
I found that not ticking “initial scale 1.0” in the mobile options has now made Firefox reduce in size to match Google Chrome. Firefox does still have the bolding fonts as you mention, so I will now add the code you have listed.
I’m not sure if unticking “initial scale 1.0” has had an effect on a mobile device as I haven’t tested yet so it might not be a fully successful solution.
But currently it is just Safari which is the weak link here. It remains quite a bit larger from the project which has been designed. Quite odd but I hope this can be resolved as its important to have it displaying consistent across all browsers.