Hey all, really looking for some help with this. I am new to trolling. Been drifting and casting since I was a kid. I recently got some 40 Tru Trips, new 8'6" rods, line counter reels, and already had spoons, harnesses, etc.

Here are my questions:
When you are trolling 40 Tru Trips, I understand the depths and how the speed works as I have a chart but what I don't know is how long of a leader do you put on your spoons or harnesses? What kind of line should I use for the leader?

2nd, how do you know when a fish is on? Is it obvious? Does the rod bend over a lot more? If you are marking fish at 23' in 30' of water, should the bait be at 17-20'?

I have read a lot and seen plenty on the internet but I'm still lost here. This may seem like a silly question but I am just trying to learn from someone who is willing to give me a few pointers. Thanks and happy fishing.