Hi @
yannis7777, in my opinion, that looks like a perfect mid-level bike that should be nice to ride for distances over 50 km. At Shimano 105, you've entered a higher tier of performance and durability in regards to componentry.
Comfort is most often decided by handlebar, grip/tape and saddle preference. The frame and components itself should be plenty comfortable. If you find yourself routinely riding longer distances, drop bars my provide more comfort as they offer more hand positions, but that would require purchasing new shifters. If you prefer the position that flat bars provide, then you should stick with a flat bar as drop bars will be too narrow.
Enjoy the bike!