I started out with a Pullrite SuperGlide 2900 auto-slider and realized I didn't need it. I upgraded to a Trailer Saver BD3 when we traded trailers. When I purchased the BD3, I still wanted a slider, so I paid the extra $500 or so for the Simple Slider. It has been sitting in the garage ever since. With both hitches, I was able to get the trailer close to level, but on both I had to run the pinbox in the shortest setting.
If the fifth wheel had a squared off cap, like an older Nuwa or Cedar Creek unit, then you would absolutely requite a slider. If it has one of the newer, rounded corner caps like my two 5'ers have had, it is optional. I cannot turn a full 90 degrees with my current setup, but can get to about 83 degrees without touching. You can only get to that angle when backing, and at slow speeds, so I just keep an eye on it. In all practicality, it isn't a limitation at all. I did accidentally crush in part of my cab when messing around with it one day trying to determine how sharp I could go, then spent a few hours the next weekend pulling the dents out with a paintless dent puller I found on Amazon, so be careful. But a slider isn't needed, and isn't worth the extra space it takes up in the bed.
Hitches come in all different grades. For us, it was worth investing in a premium hitch like the BD3. For many others, the B&W Patriots are good enough and also have a premium-type jaw.
Be cautious about rear tire weights on a SRW, especially if you have 20s. They are the weak link on our trucks so everything is derated appropriately. I had to make major upgrades to my suspension and go to 19.5" tires to safely pull my trailer with the way I have it rigged out, but you should be okay with a lot of 5'ers and your stock truck. The aux fuel tank you have is one of the things that made us go over, though, so keep that in mind.