Hi Spycather
Welcome to the forum.
Firstly Bravo - it is always great to hear from people who want to better themselves. But before someone brutally pisses on your flames, I'm just going to gently moisten the edges with a damp rag
All of the courses you are looking at will leave you in a position to apply for any role which includes First Aid. There is a lot of overlap with FAW and FPOS; FOPS is essentially FAW with oxygen and spinal management. From a good course provider it can be put into the context of your working environment, hopefully over 5 days to allow plenty of time for scenarios and heavily laden with practical, pragmatic advice to help you deal in the first instance with casualties until further help arrives.
In the worst case it will be FAW with Gun Shot Wounds, Ballistic trauma, IV therapy and who know what else crammed into three days.
MIRA is a great course specifically designed for those who are working or playing far from help to prepare them for serious trauma and offer advanced procedures where necessity dictates. This really is the worst case scenario type stuff and your interventions are warranted because without the casualty would probably die given the nature of the injury combined with the distance to definitive care. They may very well die anyway but you have given it your best shot with your limited knowledge and experience. It has no role in civilian or urban environments or when not working under the auspices of an employer who is willing to offer any type of cover for your actions. But a great course when delivered well by the likes of Exmed and Merit training.
EMT-B is a grey area; if you want to learn more (basic anatomy and physiology, Common Medical Conditions and dealing with infants, children and the elderly) it is great but you are unlikely to learn any more practical skills than on a good FPOS course or be employed off the back of it. But all good CPD if that is what you are after.
Have a read of
this article for more info on the different courses beyond FPOS
As a training provider it is not my place to comment on other TPs but this article should give you an objective guide to choosing a good
Training Provider.
HTH
Adam