#1
What does it mean by landing on stronger chord tones? Say i have a chord progression of Em Em C C B and i want to solo over it. So do i try to land on notes that are in Em,C or B? or should i land on the notes that are in Em when the Em chord is being played and land on notes that are in Cmaj when the Cmaj chord i being played?
#2
'land on the notes that are in Em when the Em chord is being played and land on notes that are in Cmaj when the Cmaj chord i being played?'

i think it might mean that
#3
The last one (Em chord tones over Em and CM chord tones over Cmaj) makes more sense to me.

Over different chords, a note will have a different amount of dissonance/consonance. But if the harmonic intervals (the space between two notes that are being played at the same time) are the same, than the level of consonance will be the same too.

For example, a B over a G chord will sound consonant, as it makes a Major third with the root note (G). But a B over a Dminor chord isnt consonant, as it makes a major sixth which is dissonant in minor chords.
And a G over a C major would sound very similar to a A played over a Dmajor chord, consonance wise, because they both use the same harmonic interval.