  Recent reports of current-induced switching of ferrimagnetic oxides coupled
to a heavy metal layer have opened realistic prospects for implementing
magnetic insulators into electrically addressable spintronic devices. However,
key aspects such as the configuration and dynamics of magnetic domain walls
driven by electrical currents in insulating oxides remain unexplored. Here, we
investigate the internal structure of the domain walls in Tm3Fe5O12 (TmIG) and
TmIG/Pt bilayers and demonstrate their efficient manipulation by spin-orbit
torques with velocities of up to 400 m s$^{-1}$ and minimal current threshold
for domain wall flow of 5 x 10$^{6}$ A cm$^{-2}$. Domain wall racetracks
embedded in TmIG are defined by the deposition of Pt current lines, which allow
us to control the domain propagation and magnetization switching in selected
regions of an extended magnetic layer. Scanning nitrogen-vacancy magnetometry
reveals that the domain walls of thin TmIG films are N\'eel walls with
left-handed chirality, with the domain wall magnetization rotating towards an
intermediate N\'eel-Bloch configuration upon deposition of Pt. These results
indicate the presence of a sizable interfacial Dzyaloshinskii-Moriya
interaction in TmIG, which leads to novel possibilities to control the
formation of chiral spin textures in magnetic insulators. Ultimately, domain
wall racetracks provide an efficient scheme to pattern the magnetic landscape
of TmIG in a fast and reversible way
