the PCE instrument editor contains three tabs: Sample, Wavetable and Macros.
for sample settings, see the Sample instrument editor.
the only differences are the lack of an "Use wavetable" option, and the presence of a "Use sample" one.
this allows you to enable and configure the Furnace wavetable synthesizer. see this page for more information.
note: on PC Engine, using the wave synth may result in clicking and/or phase resets. by default Furnace attempts to mitigate this problem though.