Reddit reviews Life in the French Foreign Legion: How to Join and What to Expect When You Get There

I don't feel qualified to answer your question directly as I haven't served in the FFL(yet), but I would recommend this book written by a veteran of the Canadian armed forces who served in the Legion from 89-94. Some of the information is probably a bit dated by now but It does a great job of giving you practical information. Even in today's internet age there isn't much hard information out there about what to expect from the Legion and IMO his book is the most useful resource I have found yet.

He discusses this subject in the book and he says that there are a lot of things that the FFL does differently from most military units that veterans of most other services would find objectionable. He warns the reader, especially veterans, to be ready to accept some pretty large departures from usual military doctrine. For example, it is apparently commonplace for NCOs to hand off their weapons to their subordinates for cleaning after range time. He also talks about how the language barrier can be a hindrance to a unit's performance. In one instance while he was deployed in Chad, a Legionnaire was given an order not to fire his weapon while on guard post under any circumstance unless getting it cleared first. He had misunderstood the order to mean that he could fire at anything WITHOUT clearance, and ended up causing an unfortunate situation for him and his unit. It's not all bad though. He praises the extremely strong bond that the between legionnaires that the Legion fosters, and acknowledges that when the fighting gets thick it is these type of familial bonds that can pull a unit through a tough situation.