I recently got a new qrp rig;
https://www.youtube.com/watch?v=m5le1ZFcGE8not me, just an example
Prior to that had a Ten Tec 509 I never made a contact with, and a few years ago had a Icom 703. The 509 and 703 are similar in power out, with the Icom having a transmatch built in. The Icom matched a few loops of wire around a window frame in the bedroom providing for ssb contacts with Michigan and elsewhere, the 703s a nice rig but the finals are sensitive and I am brutish to equipment, so you know how that went.
The G90 has much tougher finals as well as a wideband transmatch with the addition of a full 20w out and of course the tiny fish finder.
In cw work, 5w will in many cases make over 90 percent of contacts heard, where 1w will be heard only 10 percent of the time.
The corollary to ssb work is 20w will give you about 90 percent heard call success, where 5w will only be about 10 percent successful.
Cw has other advantages for low power work as many cw ops use headsets rather than a desktop speaker, allowing for better sound detail and noise negation, and the obvious benefit of concentration of energy within a few hundred Hz of filter bandwidth.