Unloading and camper support

Just the jacks would work. Lower the camper as far as possible.
However, that is pretty hard on the jack mounts and there will be some sway.
If you can support the camper base in one of the ways you described, you can eliminate all sway and all bending forces from the jacks. After you have supported the base and lowered the camper onto the supports, just lift each jack gently until it is barely free from the ground to remove any built up tension, then drop it again without lifting the camper.
There is also a product called Wobble Stoppers by Torklift that adds additional bracing to the jacks and eliminates sway without supports underneath the camper.

Edit: The camper is 15 years old - the front jack mounts may not be as solid as they once were. Or they may be as good as new - I don't know your camper.

We use these and it stops the wobble.

http://www.camco.net/rv-stabilization/stack-jacks-stabilizing-trailer-jack-stands-2per-boxbilingual-44562

That is what I have been using as well. Inexpensive & reliable.

Cinder blocks and a sheet of 3/4" plywood works too.

If we are staying more than a couple days we always unload, first level with the camper jacks then tighten up on the screw jacks until tight. Never had trouble with stability.

“or just use the jacks?”

Not the best practice. Stabilization only.

I use 2x4’s and sawhorse brackets. And a 3/4” plywood from my truck bed then set the camper on them.

We did 3 months with the camper off the truck. Lower the jacks to maintain clearance for sewer hose connection. Then we placed 3 lynx levelers and 1 leveler cap under each of the 4 aluminum stacker jacks. On top of the jacks a 4x4 the width of the camper bottom with carpeting glued on the contact side. On the jack side, drill holes to accept jack heads about 1/2” deep. All items store in the camper basement when traveling. Kept the camper very stable. Jacks need re tightening after settling

Bob

I used Camco Aluminum Stack Jacks with a board on the top and bottom. $31 from Amazon and relatively small since they stack.

Built my own support system, works on semi uneven ground and takes up no room to haul.