There appears to be something fundamentally wrong happening here with the image content, and the camera settings appear to have been chosen oppositely to what is intuitive. Substantially more information is needed to make full comment - camera settings (noise reduction, any anti shake, , tripod?, through glass?, path from camera to each image.
It seems that to a reasonable extent changes in ISO performance may have been masked by camera settings. The image content change is hard to understand. It's conceivable that whatever " program developed" these jpgs from the raw image (whether in camera or externally) did so "creatively".
Pixel peeping suggests that the 1600 ISO image is both sharper and has more fine detail in places.
Aim of the groups of finer "runs" of paint are different between photos. Not just more detail or less detail relatively bur different detail - eg a loop of 'paint' on one run appears to have appeared on a different run.
In addition, the low ISO picture has a darker band at the bottom (about 20% of height) and has reflections in it. The illumination changes at top left and top right (brighter on 160 ISO image). Both photos have highlights blown in areas around the lights (higher on 160 ISO) mostly in the red channel.
Somewhat unexpectedly, the EXIFs report 160 ISO = f/22 and 8 seconds (NOT 1/8) and the 1600 ISO reports f/4 and 1/40th second. These correspond to exposures of withing 6% of each other indicating that the figures are probably correct. For meaningful comparisons I'd have expected constant aperture and shutter speeds scaled the other way eg
f/4, 1/40th. ISO 1600 and
f/4, 1/400th, ISO 160.
Better still, as long as a tripod was used, would be to reduce aperture to get better depth of field and use longer exposure times - say f/11 and about 1/4s and 1/40s.