I can't really comment on any of the cg balance devices as I have never used one. I've always used my fingers and never had a problem at any time. It may not be pin point accuracy of a purpose made machine, but it is close enough to fly the model and adjust after flying. Either more weight forward or rearwards.
I've always used my fingers and never had a problem at any time.
Best wash your hands before dinner.
(Punch line to an old adolescent joke .......................... "By the grace of God and with a little help from these two fingers, I got it all back in." If you don't know the joke, it's OK. It was a groaner anyway.)