The main effect of the ranked wingtips is not improving the glider performance but change handling characteristics during thermaling. Such wing tip changes the stall pattern of the inboard wing during the circling in a thermal. They are optional.
- Whit this wingtip installed, you should be able to climb better in weaker thermal. Due to a change in the wing stall pattern and bigger area.
- Glider should have a higher glide ratio at a lower speed. Thanks to the higher aspect ratio. See. this answer https://aviation.stackexchange.com/a/8797/54674
Such wing tips adversely affect roll rate. Especially if you need to quickly change your bank angle in "wild thermals".
In theory, they should decrease your glide performance characteristics in high sped flight.
It is always a pilot choice. Glider looks much better with them ;)
Parasitic drag is caused by the tip vortices that spill off the wingtips. With a rectangular wing with no washout, the pressure difference between the upper and lower surfaces will be more or less constant across the entire wing and so the vortices will be large. With a tapered wing and washout towards the tips, most lift is generated near the root and so there’s less pressure difference near the tips and hence the vortices are smaller. Adding the raked sections in the photo will help a little more but it’s hard to say whether it will make a measurable difference. It would certainly be better than abruptly terminating the wing at the last batten.