Two Solver Questions

1. What’s the best solver for someone who plays exclusively mid-stakes live full-ring with all that implies (loose ranges, multi-way pots, etc)?

2. I’m part way through Nick Petrangelo’s smash live cash course on Upswing. Most of the charts and solver stuff make obvious sense, but does anyone know why the solver likes K6s so much? I get that it blocks AK/KK but it has awful playability.

Thanks