KE6MAK has got this right, the feedline and unun are pointless junk if you still need to use an atu. Choose a wire length that avoids the impedance extremes on the bands you want operate, throw out between 2 and 4 radials on the ground and plug straight in. As long as you are not matching an antenna that is way too short the losses will be low.
With my KX2 I use 4 x radials 7.5m long
6m travel pole
40/30/20m 9m wire, inverted L 6m up and 3m out
30/20/17m 7.2m wire wrapped round the pole
17m - 10m 4.5m wire vertical
These lengths all range between just under a quarter wave to just under a half wave so avoid the impedance extremes and give low angle radiation. The vertical is a good performer for SOTA, even with very poor ground and limited radials. The HB9SOTA antenna tests demonstrated this in the tests below.
Horizontal antennas do have ground reflection gain, but this is all at too high an angle to be useful on 40m and above. 40m doesnt provide NVIS at higher latitudes except around solar maxima, so no help to most of us currently.You may of course get low angle gain from a low dipole, but you need to be very near steeply sloping gound. You can model this using HFTA which comes with the later ARRL Antenna handbooks, my conclusions were you need to be on the edge of the sloping ground to get a significant advantage.