I went a while not using decoys but moved toward them again last year. Have had great success with them. I bought a jake and hen and use them together all the time. I will say they have worked well this year for sure.
I use a feeding hen and just a regular upright flextone decoys (They look great). I setup with them about 15 yards behind me and position myself where I think the birds will come from. If possible I always like using decoys because I feel like it gets eyes off of me and allows me to move more and get my bead on their head without them catching the movement.
Like calling (how, when, frequency) it boils down to what the turkey is doing.
On 5/9 I killed a gobbler that came in looking to fight. He and a running buddy responded to gobbler calls that morning. I had decided to use a jake decoy because of an encounter with a subordinate bird the morning before. 90% of the calls I made were gobbler/jake sounds and they ate it up.
One year in KS a friend and I were scouting a farm and watched a gobbler run jakes off all afternoon. We used a jake the next morning and had a quick hunt.
The only hard and fast rule I have is to adapt to the situation and hunt accordingly.