Nice tutorials showing the potential the renoise sampler.
For the karplus strong sound, I managed to (perfectly!) tune the multitap delay with a formula device. The highest note is below c6 though, as 1ms is the minimum delay. Look for my ktrk doofer presets, the “Multitap Delay” preset is what tunes the effect like you used it in the video. Just load the preset, and add and assign some macros to the doofer to control the feedback and the filter. You can also adjust the tuning in the formula device, i.e. use transpose, tune to a harmonic, or change the base frequency.