If possible use lookup or better cluster + lookup if you have reasonable existing metadata. This will usually yield better results, as it can actually match to the proper release. AcoustId lookup only looks at the audio and therefor has no knowledge which release would match what you have.
Also cluster + lookup deals first on a release then on a track by track basis, so it will try to keep tracks together. AcoustId lookups look at each file independently, hence it is more likely to scatter files across releases.
btw, here are my slider settings:
See how I lowered most types I don’t care about and raised album. One difference to IvanDobsky’s settings above that I have mostly albums and nearly no singles, so I prefer albums, then EPs and singles are basically at default settings. Ivan on the opposite seems to be more interested in EPs and singles, thus he raised that one more than albums.
The ticket is https://tickets.metabrainz.org/browse/PICARD-1444, and the conversation is at Please test new Picard Windows builds - #50 by Billy_Yank
My actually preferred suggestion was yours, which basically is having a selection with a colored bar to indicate more or less. But that’s actually kind of what we already have 
The improvement would be to use a limited number of steps for the sliders, as the fine granularity they currently provide is a bit misleading.