Yes, I was first going to see if the CGA out to TV met my needs first. However, I'm not optimistic because some of the games I was looking to use rely on 80 column text.
I have my 5150 connected to a TV with an RF modulator. With that setup, you'll go blind looking at 80-column text. I used the computer like that for over three months before I finally got a Tandy CM-11 on Ebay. Hopefully your TV has composite inputs. 80-column text will be a little better with a straight composite connection, but you really need a RGB monitor for it. Some TVs unfortunately have an off-centered picture (like this one I'm using) due to bad adjustment at the factory. DOS provides a variant of the MODE command that loads a TSR to keep the picture centered, but you can't use it on booter games.
The first thing you'll notice about the composite output is the color bleed, which causes everything to be filled with artifact colors. Some games (Archon, Ms. Pac-Man, most Sierra games) use this to give a 16-color display that would be impossible on a RGB monitor. Games also sometimes use the cyan-red-white palette, which appears in grayscale on composite monitors. In summary, you need both a composite and a RGB display to fully utilize the CGA card's capabilities.
It was quite common for games to write directly to the CGA registers. Even many games that had EGA and VGA support would do such things in CGA mode. The various tricks that mess up EGA/VGA cards include:
* Changing the color palette by writing directly to port 3D9h instead of using BIOS function 10h 0Bh
* Use of the cyan-red-white palette (just appears as cyan-magenta-white on EGA/VGA)
* Tweaking the horizontal and vertical position registers to shake the screen
* Raster tricks (eg. Frogger)
* Use of the 160x100 pseudographics mode (but can be fixed by simply tweaking the maximum scan line register)
* Sierra's favorite trick of setting composite mode by switching to 320x200 graphics and then writing a 1Ah to port 3D8h to set 640x200 graphics with the color burst enabled (to dupe the BIOS into printing 40-column text)
* Setting the normal 320x200 graphics by writing directly to the registers (Digger does this)
Still others like Troll's Tale and Microsoft Decathlon produce a split-screen effect on VGA. I'm not sure why this is. One or two like Jungle Hunt and Moon Patrol simply lock up on VGA and aren't playable at all.
As far as Hercules is concerned, it is 6845-based just like CGA. The video memory in its graphics mode is interlaced in the same manner as CGA, but with four rather than two banks of scan lines. Programs like SIMCGA just rearrange the CGA graphics data to fit in the Hercules' memory properly.