The only fixed roster is 9/5 which is generally popular with commuters but it takes a while to get onto that. 8/6 was talked about 15 years ago and there has been some discussion recently but I wouldn’t hold my breath. My ref to 3/6 is that duties are usually between 3&6 days long followed by days off. People make the commuting work - I did it for a year from Toulouse and it worked but was hard work. Bru is doable because people do it successfully!
You don’t say what your other job options are, if any.
My advice (feel free to ignore) would be go for the interview and ask all these questions. The recruiters are very approachable. We are recruiting strongly but don’t want you to join and then 6 months down the road go elsewhere because it doesn’t work for you for the sake of a couple of unasked questions.
dh