I've only done the sections from Woolum to Richland Creek Campground (20+ miles) and from Lick Branch to White Rock Mountain (38 miles). Both are great, and I doubt you can go wrong with any part of the trail. Lick Branch to White Rock is a lot of up and down, 1000 feet at a time, so if you want something "easy" that's not it. I'm pretty sure the Ozark Highlands Trail Guidebook has elevation graphs if that factors into your decision.
I don't know about the fishing, since I don't fish. The trail ends at the Buffalo River, and there is a trail off the OHT at White Rock Mountain going to Shores Lake, which I would guess is a fishing spot. I don't remember if the OHT Guidebook has any info about fishing.