Start with the vocal
In most song-based music, the vocal is carrying language, melody and emotional focus at the same time. Guitar parts that continually occupy the same register or rhythmic density can make the vocalist work harder without anyone consciously knowing why.
Choose a register with intention
A capo, inversion, partial chord or higher voicing can separate two guitars far more effectively than changing tone. Arrangement begins with musical space before it reaches EQ.
Rhythm is often more important than notes
The right subdivision can make a chorus lift or a verse settle. Two players using the same chord tones can feel completely different depending on where they place attacks, how long notes ring and whether they reinforce or counter the drums.
Let sections earn additional layers
If every guitar arrives in the first verse, there is nowhere for the arrangement to grow. Holding back a texture, octave, double or ambient layer can create a more meaningful change later than simply turning everything up.
Tone follows function
A guitar that is meant to create pulse may need definition. A guitar that exists as atmosphere may need to blend. Choosing tone before deciding function often leads to beautiful sounds that do not solve the arrangement.
Restraint is a professional skill
Players are often hired because they can do a lot. They are rehired because they know what not to do. A part that leaves the artist sounding more like themselves is usually more valuable than one that advertises the player.
Next step
If this is the problem you are trying to solve in a current song, you do not need to wait until the project is polished. Send Sven the demo and explain where the decision feels unclear.