Several years back, NewRisingSun discovered a means of enabling "TGA-like" compatibility with some specific VGA chipsets. Regrettably, neither video chipset of the two RLX variants is compatible with the method involved.
That said, many popular titles with Tandy sound support will automatically detect and leverage that in tandem with the VGA/EGA graphics of the RLX (or can be explicitly configured as such), while several others can be coaxed into it otherwise. There are exceptions, of course. Which games are giving you trouble?