It depends on the collar and fabric.
For Barba BD I get light unfused lining for both collar band and tips.
For Broke and Bespoke BD I get medium unfused lining for collar band and light unfused lining for tips.
For my own collar, which is similar to the 1738 collar (see the collar spreadsheet) I get medium fusing for the collar band and and the tips.
Personally, for non-BD collars I would usually get medium fusing for the collar band (maybe with an exception for...