I need a foundation for a smaller shed. Floating wood deck?

I could use some feedback on how to build a foundation for a 7 x 7 resin garden shed, so that it's flush with an existing wood deck (the shed doors will be facing that deck for direct access). Here's some pix of the site with the shed floor showing roughly where it will sit. (I'm planning to knock out the stone wall).

From what I've seen online, there are at least two options:

One, a floating wood deck that rests on either skids or posts set in concrete blocks.

or Two, a "ground box" made of PT posts built into the ground and topped with a gravel bed. I'm not keen on this "box" option because it looks like way more physical labour, plus it's not moveable.

So I'm leaning toward a deck like the one that's already built but that's supported by adjustable post saddles like this guy so I can fine tune the height to match the existing deck (and adjust for any potential settling in the future).

Issues:

1. This is in the PNW so lots of rain, but freeze/thaw cycles are rare, we do occasionally get a decent snow dump but it only lasts a few days.

2. Will a wood deck with a post in each corner be enough support, or will it need more? The shed will store lighter items like patio furniture, BBQ, wheelbarrow, shovels, hoses, etc. so 500 ish pounds. I'm wondering about setting a fifth block in the dead center that's slightly higher, maybe 1/4" to 1/2", so any pooling water drains toward the perimeter.

3. Should the two decks be attached or independent? I can see arguments either way.

TIA