I wouldn’t feel less safe in the cabriolet version.
However, I would feel frustration that the agile, competition proven, BMW engineered and built car was hampered by the reduction in rigidity and increase in mass caused by cutting the roof off.
A capable performer has been reduced to a car for poncy, pink purse carrying, spray tanned, chihuahua doting, student daughters.
When you say “safe” I assume you mean crashworthyness.
I don’t think it’s safe to be seen in.