The above post title equals......challenge !
Yes, when band conditions are at there best, QRP serves just as well as the 100 watt stations.
However at solar flux or band lows, QRP becomes a bit of a task.
No matter the band conditions, THE great equalizer is the antenna. Putting up the highest, resonant antenna can make all the difference in getting the contact in the log.
I do use an 8 element beam here regularly. However low dipoles and compromise verticals are used as well.
I have learned in recent months that QRP and Mobile operating is quite the challenge too.
Recent efforts using an FT817 and a ATAS-120 , mobile...have been in vain. (no Joy)
So as the solar numbers continue to decline, plan accordingly, and fine tune or improve your antenna farm to gain the most from operating at 5 watts or less.