Oh I see about the cassok. Did not pay attention to that. Dangerous to be outside with it in the "friendly world we live in"?
Not at all, especially not in England now. The streets are full of men in "robes" - Greek and Russian Orthodox, mullahs, imams, perhaps even a druid or two? (Also, the SSPX lay brothers here seem to wear cassocks all the time - perhaps because it's their religious habit.)
I think it is important. The Archbishop insisted on it from the beginning for the students in Fribourg in 1969, even though the less confident found it difficult and even alarming, as they were the only ones dressed like that in the whole university. (Mentioned in +Tissier's biography of ABL.)
It's a sad fact that from the beginning the priests of the GB District have worn suits in public. I don't know why. One reason I heard was that otherwise people would think they were High Anglicans! But Anglicans in cassocks must be as rare as hen's teeth now.
The 1970's-style black shirt with "visiting card" collar just says "Vatican II priest". My older Protestant relations say they expect Catholic priests to wear cassocks and are very surprised the SSPX doesn't. They remember them in the streets before Vatican II. (Not all wore them, certainly, but the ones who wore suits were taken to be Protestants, so weren't noticed!)
But a cassock does preach a sermon. The French SSPX priests stationed in England refused to wear suits. Fr. Eric Simonot was in Wimbledon in the 80's and he said it was a wonderful way of getting to talk to people. They would stop him in the street or talk to him in shops and he was able to tell them who he was and what he doing. A chance the others are missing.
Do the SSPX priests in America wear cassocks in public?