like others said, for games and other non OS-friendly apps, a scandoubler is required - note that a graphics card will NOT allow you to watch games on a vga screen, unless it has some sort of a pass through and internal sd (only some Zorro cards had those AFAIK)
The good news is that when in Workbench, you can use a little utility called ModePro (it has been more than 10 years since I used it, so don't ask me how) to "force" apps that open their own screens into a particular graphics mode - the downside is that it does not always work, but it should do in most cases (like watching pics etc)
a TFT-TV is among the best solutions - though I find that switching from vga to scart and back can be tiresome.
