There are a few very good crappie in the main body of White Rock Lake year round, but you have to look hard until you define the patterns. I fish my kayak there regularly, but release all my catch there now because of the recent decline.
For the record the outboard motor limit on the lake is 10.5 HP. You can launch any boat with a bigger motor and just navigate with your trolling motor. https://tpwd.texas.gov/fishboat/fish/recreational/lakes/white_rock/access.phtml
Commercialized, wholesale bait consumption has greatly reduced the shad population. On numerous occasions, I have seen multiple five gallon buckets filled with shad collected in the shallows during the winter to be frozen for catfishing. There are even guided "bait trips" done commercially in the fall/winter now. Combine that with the numerous brushes with low oxygen during the recent years droughts and the shad (and therefore crappie) population has been really stressed.