Impact on Beamlines

No.
The gains depend strongly on each beamline’s optical layout, photon energy range, and measurement approach. However, undulator beamlines can be grouped into three broad categories that each benefit in distinct ways:

• Beamlines using a secondary source aperture gain more intensity for a given slit size
• Beamlines that directly image the source gain proportionally smaller focal spots without flux loss
• Beamlines that weakly focus or do not focus the beam gain a more coherent, parallel beam.

Relative gains are generally larger at higher photon energies. Benefits are most significant for hard X-ray beamlines, while soft X-ray beamlines already operate near the diffraction limit and will see more moderate improvements in coherent flux, but will get the largest coherent fraction in absolute value.

Yes, though differently from hard X-ray beamlines.
MAX IV is already diffraction-limited in soft X-rays (up to approximately 330 eV with the current emittance). MAX 4^U extends this diffraction-limited performance up to approximately 2 keV, significantly expanding the tender X-ray range and delivering meaningful gains in coherent flux for scattering techniques at soft X-ray beamlines.