I agree with the cabbage spacing being closer. Obviously it depends on the cultivar and how long they stay in the ground but when we plant them 30cm apart we get slightly smaller cabbage heads but having many more plants makes up for the smaller heads. I actually prefer smaller heads as they are more manageable in the kitchen.
I think it would be good if you could start a video reminding viewers where you are, zone, etc.. and the time of year you are doing this project, etc.. I always appreciate your tips.
No I did not because I did not heat my greenhouse this year unless it got below freezing and my mandarin and lemon need it. So they were used to the cold. They went straight into the beds.