IME carbon posts do make a difference to comfort compared with alu. However, the shorter they are the less difference they make and some make more of a difference than others.
I haven't tried a ti seatpost though, so can't comment on that.
TBH this all comes down to your budget. Cutting out the stem and post and going for cheap wheels now would drop a lot of the cost if you needed to. If you don't then just go with what you like the look of best and will make you enjoy the bike. It's going to be great whatever.
IME carbon posts do make a difference to comfort compared with alu. However, the shorter they are the less difference they make and some make more of a difference than others.
I haven't tried a ti seatpost though, so can't comment on that.
TBH this all comes down to your budget. Cutting out the stem and post and going for cheap wheels now would drop a lot of the cost if you needed to. If you don't then just go with what you like the look of best and will make you enjoy the bike. It's going to be great whatever.