The difference is gear ratio and how you and your Jeep drive with your setup. 89 2.5L with 33s on the slow trails near you I may use 4L. It gives me better speed control no braking just use the engine. Easier to start off the e-brake after a stop on a hill or the flat. When I can get some speed I run 4H usually maintained or semi maintained trails. It is a choice you make. Look in 4L you aren't running many stretches of the trail above 20 mph. So you pick a range by the speed and difficulty of the trail. Love it in the rocks great control.
I have a smittybilt phone app inclinometer not perfect but -40 and +50 degrees it goes into the yellow. So you be the judge it is your Jeep. Your stomach should tell you when you have had enough. However if you are going to run some steep downhills that is what a stinger is for on the front bumper. Photo attached of why and how it works.
Get out on the trails and get a feel for your Jeep. In your configuration it is a highly capable off-road vehicle and when you know the limitations and decide what more you want your Jeep to do you will then be able to plot, plan and purchase the things you need.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
AF Jeep Club Tail Number 184