Passive solar porch

I just wanted to pick people's brains, get some ideas:

My wife and I are buying our first house, a small-ish two bedroom place in urban Hamilton, Ontario, Canada (zone 6-ish). Previously we've rented urban apartments and wwoofed, so we're pretty excited about 'owning' a chunk of land and making it our own, even if it's not yet the multi-acre homestead we want asap.

We found an accidentally special house: the front of the house faces south, and has a glassed-in/covered porch/sunroom (small-ish space, maybe 5'x20' which only gets shaded in the late afternoon. Of course my immediate thoughts are "Hey, it's already a functional passive solar greenhouse." I've been thinking about ways to make it more functional on the cheap (when we would move in in 3 months), this is the list so far:

-either on the inside or outside of the windows, install 6mm greenhouse plastic (using track and wiggle wire), because the current windows are only single pane

-plant something deciduous to provide summer shade. Maybe shrubs/trees like sumac, lilacs, serviceberry, hawthorns, semi-dwarf fruit trees; maybe even have some king of trellis standing in front of (or attached to the sides and top of) the porch for some vines be it grapes, goji berries, curcubits (squash, melons), hops, morning glory, etc.

- inside, have a few shelves / tables for seedling production and a few medium to large pots for year round herbs, greens, exotic novelties

- up against the wall between the "porch" and the interior of the house, some kind of water storage system be it barrels, buckets, rubber maid bins, bottles etc for thermal mass (probably using the water containes as the base for seedling shelves/tables. Probably bags of potting mix ingredients and my worm compost bin to add to the clutter and thermal mass.

Of course one of my limitations is that the porch is an indoor "finished" space. I would need to keep moisture down (careful watering) to avoid any mold or water damage.
Also I am not sure that the ceiling or walls are well insulated (will find out during home inspection this week).

Any ideas, tips?

You might consider interior storm windows, which would be tidier, and better insulating.

Black Pickle barrels make great support structure / thermal mass. 40-50 gallons.

I suspect that any greenhouse, can be assumed to be more humid than the dewpoint of the house (thus causing condensation), at some point during the year. Plan on that. Venting must be considered. Every drop of water you use to water a plant is going to go somewhere, only a tiny fraction gets made into plant.

5'x 20' glassed in porches become 'storage' in short order if you aren't vigilant about it.

Black barrels as table/counter legs, since you have very little room to work with. Build the wall like cinderblock shelving, but with the barrels instead of blocks. You don't really have enough room for 55 gallon drums, so I don't know what smaller container you can find cost effectively.

Topher's interior storm windows are tidier and easy to pull one or two off for ventilation when needed for warm winter days. But you can do lathe strips outside cheaper than wiggle wire, and just as easy to reuse.

Outside sun shades for temp control in the summer. You can buy them cheap from costco or sam's if you have them, or make your own using shadecloth, or buy from amazon. Or awnings with proper overhang for passive solar in your area. In addition to deciduous shade.