When connected through RGB it does not matter if the signal is 50 or 60 Hz, your TV will support both.
However for a composite connection it is always hardwired to either NTSC (Japan/US 60 Hz) or PAL (Europe 50 Hz). If you switch the VDP to the non-default frequency for your machine (only possible MSX2 or higher) the RGB output will work fine, but the composite output will display in black/white or not work at all.
Afaik think the Sanyo PHC-23J uses a standard RGB connector. What inputs does your TV have, though? In Europe we have SCART and in Japan they have the JP-21 connector, but I don’t know about US TVs. If it has HDMI then you can use an RGB DIN -> SCART cable (sold on e.g. retrocables.es) and pass it through a cheap SCART to HDMI converter (sold on eBay, Amazon, etc.).
p.s. RGB will also give a much better image quality compared to composite video.
