All secondary concerns. If it doesn’t fit properly, ventilation is irrelevant. If there’s a pressure point on you forehead, it really doesn’t matter how easy it is to fit a light. Etc.
All valid concerns, but all secondary to fit
Yes, but still very much part of buying a helmet.
I found three MTB helmets that all fitted very well and discounted one immediately (TLD A1) because everyone reported how hot it ran.
Of course fit is important, but let’s give people some credit and try and be a bit more helpful with personal experiences and opinions, huh?
I’m in exactly the same predicament as the OP, and I keep seeing exactly the same unhelpful responses when going though old threads on here, often from the same people.