Pecan will be fine for the smoke. I do hot smoked catfish at 250-300° until the fish flakes easily. For catfish, you may be OK with it on the grates, but I highly recommend that you use a fish basket for the catfish and DEFINITELY for the crappie. Both will easily fall to pieces if you aren't careful.
Another way I've done it with out the baskets is to make a small tray out of heavy aluminum foil. Lay the fillet into the tray, add some seasonings and maybe a pat of butter to the tray and then smoke.
As a "rub" for the fish, I always slather them with a thin layer of EVOO or spray with Pam, and then add my seasoning of choice. Wife likes it with lemon pepper, I like it with Tony's.