Can't comment on sportful but I've had a pair of dhb winter bibs for years and they are toasty. They are padless so worn with another pair of shorts underneath which means extra warmth. That said I'd try then on if you can and go for which is comfier.
As for baselayers; Rapha for Merino - yes they are worth the extra.
For non merino I have a helly Hanson lifa dry long sleeve that is very warm when under a jersey/jacket but non warm like merino when standing still.