Back to the OP. I love 5ers, I had a three month driving school with them, and never drove a bumper pull until I was over 40. I wouldn't have anything else.
For the fifth wheel, if it is rated for your pin and trailer weight, they will all work. The head should articulate backy/fronty and left/right. I like a slider, because with the articulation it can help you in a tight spot.
I like rails, but I have ratchet straps that fit the slots and I tie stuff down. I do not haul gravel or sand and I could care less about a flat bed.
Slide bar verses jaws (dual or single). The bar has more movement, but it is less likely to fail than the kingpin, they should cost a lot less. Jaws have less movement, but have wear parts inside. Both get the job done.
When you hook up do a pull test. Then when before you dolly up and hook up the emergency and plug, look to see if you have captured the pin. Use a flashlight if required. I then lock my fifth wheel so no joker can release my pin when I am using the bathroom.
Don't overthink, you can change your mind later without it costing too much money. Checklists are a great idea, and do it the right way, the same way, each and every time. Do not let others distract you.
I use an articulated slide bar, with a slider on rails. But that is just me, and I like simple. Having driven less than truck load tankers I am used to a lively ride, so I dismiss chucking issues and we have visited all of the states save HI and AK by land yacht. Have fun, don't worry.