None of the two approaches are ideal: The gap fill may produce short segments of widely differing extrusion rates, while over-extruding may produce bulges on thin walls. The classic way of handling narrow regions is to either not generate the innermost perimeter that does not quite fit, but to fill the remaining region with a gap fill algorithm, or to over-extrude the innermost perimeter. Namely, thin regions cannot be filled with an integer number of fixed width extrusion lines. However this simple algorithm does not handle thin regions well, as reported in these issues. This was also the default algorithm in previous PrusaSlicer versions. The 'classic' strategy for calculating perimeter extrusion paths is to offset contours of an object slice inwards by a constant extrusion width, one offset per perimeter.
To let you enjoy the alpha without worries, the alpha builds save their profiles into PrusaSlicer-alpha directory, so you may use the alpha side by side with the current release without ruining your production configuration. Big thanks to Ultimaker for keeping Cura open source and big kudos to Cura development team led by to for his research and majority of the Arachne implementation and to and for the lightning infill implementation.
The Arachne perimeter generator was implemented based on the paper, while the lightning infill was implemented based on. The new perimeter generator Arachne and the new lightning infill were ported from Cura. This is the first public alpha release of PrusaSlicer 2.5.0 (alpha1 was not public), introducing new perimeter generator Arachne, improved seam placement based on visibility, pressure equalizer, lightning infill and several more improvements and bugfixes.