Hi JM,
The Perry plastic Light Dragoons are absolutely fine for Light Dragoons from about 1794 onward, provided you use the legs with breeches and boots, rather than the overall-covered legs. I wish they'd been available when we did our Fishguard game, as we wouldn't have to have converted plastic French Hussars for the job...
For the purists, the dolman was very slightly longer during the 1790s, as it extended down over the hips - it was shortened to waist-length sometime around 1800ish.
In the early 1790s the jacket was very different, being longer and having criss-cross braid down the front. This was replaced by the more familiar dolman sometime around 1793/94. My apologies for the vague dates - I'm working from memory.
If you're doing Fencibles and Yeomanry, many of them were identical to the regulars in terms of uniform style (albeit some in red rather than blue), though some regiments lacked the hussar- braid and simply had the three rows of buttons down the front of the jacket (sometimes with a 'frame' of lace around the buttons).