I would agree that a common musk or striped mud is the best choice, followed closely by the smaller subspecies of painted turtles. Both are hardy and stay relatively small (3-stripes usually under 4-5", stinkpots under 5", southern and midland painteds almost always under 6").
I would say that Malaysian Boxies need more room than the person in question is willing to provide, seeing as they average around 8" and can get quite a bit larger.
In my opinion, North American box turtles (terrapene) and all tortoises should be kept A.) in an non-glass enclosure, as they tend to be more stressed in glass enclosures, and B.) in a much larger footprint than a 75g would provide. Glass enclosures often just don't suit the sort of temperature and habitat variants needed to properly care for these creatures.
Josh