Honestly I dont notice any higher defense or what so ever on my necromantic creature even though I had finish upgrading the necromancer ring. My creature stats still looks fully base on limb parts I choose. Major difference I think between choices are the quests and rewards which your trainer provide you with
For slowpokex2, Kali fortress is actually in River Town. Open your Fjords map and go to the direction of River Town and you will see a cut scene and that kali fortress. Geshniz is Broken Valley. If you fully clear out entire Broken Valley, you shouldnt had miss him. Barnabus is in 1 of the cave in Fjords, which I already forget the exact location. Regarding Radcliff really clueless, since I didnt choose him