Previously there was a rubber gasket installed with a bead of RTV between the pan and gasket, mating plain rubber to the transmission.
When changing the filter the pan only needed to be dropped enough to remove and change the filter. The rubber gasket could be re-used without applying new sealant.
The new Wix filter came with a cork gasket, the old rubber appeared to be getting old after being reused multiple times so I pulled the pan and installed the Wix cork gasket with some copper RTV on both sides ...
The cork gasket became squished and flattened out, (where the rubber one held its shape). Cork gaskets can sometimes be reused if not damaged, but I think rubber besides not loosing its shape would also have better resistance to oil, chemicals, salts, etc. and last longer.
After ordering the ATP RG-31 from Rock Auto I will try using a RTV on one side similar to how the previous one was installed. ( looking for any leaks after installation,)
Hand tightening bolts sometimes work if you can get the right torque for the number of bolts, gasket material and sealant type.
OE Torque specs from a 99 XJ FSM for the 19 pan bolts and gasket materials is around 5 ft/lbs or 6–8 N·m (53–70 in. lbs.)
Jeep parts manual shows the original OEM part as a Chrysler RTV sealant, that may have been sometimes used with a thin plastic gasket that held the sealant in place on both sides for installation purposes.
As one person noted, having loose sealant floating around inside the transmission might not be a good idea
I also found a small Wix magnetic filter installed inline near the external cooler. Inline filters can be found for around $15.00 .. provides additional filtering and helps filters out additional loose debris that might be dislodged or added after a flush, oil change, etc.
I have done a couple of passive flushes one at around ~125,000 and another around ~190,000 miles replacing most of the ATF ... mostly for preventative maintenance purposes.
Theoretically ATF should not require a complete flush for the life of the transmission .. i.e. if the ATF and filter has been changed regularly every ~12,000 to ~30,000 miles depending on type of use, i.e. severe to normal duty ..