There is more to jades than just typical green leaved plant you can see everywhere, Crassula ovata. Check out C. o. Hobbit, Gollum, Crosby's compact, Tricolor, Blue waves....and many more for different leaf shapes and coloring. If you type just crassula, you'll see many different looking plants. Most of them will reproduce easily from leaf cuttings (and stem cuttings too).

If you like more rosette types, check out Echeverias. May will also reproduce from leafs, some will not but they will have offsets and also you can reproduce from stem cuttings.

Leggy plants, if otherwise healthy, will likely respond well to be-heading. You could pot the cut off top section, and leave stem with roots potted - many will grow offsets along the stem. These could be removed once big enough (or left to grow as is - anyway you like it).

Kalanchoes are very easily propagated from leaves (depending where you live, some could be a nuisance :) since they propagate so easily). There are many very nice kalanchoes there besides the 'florist kalanchoe' that are available in stores by hundreds, in many different flower colors.

Keeping plants in original soil usually creates problems because most are grown in peat - ad it isn't easy to keep it 'just right' as moisture goes. But week or even few should not be a big problem, unless it is soaking wet from improper watering in the store. They all require very good drainage, so using gravely/gritty type of substrate is beneficial to plants in the long run.

No plants like to be pot-bound (even if you read so very often...). Succulents, in their natural habitat, grow often in very tight spots/crevices and ppl assume they like to be squeezed, pot bound. But their roots, if can't grow wider, may grow quite deep in nature. In cultivation, pots approx. 1" bigger in diameter than the root ball are used most often (just a general suggestion). It is recommended to use smaller pots if the soil is more water retaining = takes longer to dry up. More soil there is, longer plant sits with 'wet feet' and that creates most problems with succulents. Typically, succulents do not need to be repotted often. But many will tolerate moving them around as you described...these are plants (unfortunately) that are often handled/used as an decorative piece, easily replaced, and often put in inappropriate containers (like terrariums, glass bowls...). So it may depend also on you and what you expect from the plants :)

I know that aquarium water is used for watering plants. What I would worry about is giving plants unbalanced 'fertilizer'; too much of 1 ingredient, not enough of others may create more problems than no fertilizer at all. Many ppl do not fertilize succulents (they live in quite poor/lean substrates in their habitat), others do. But well balanced fertilizer is much better IMO. And over fertilizing, even if using balanced fertilizer, will eventually create some problems too (too much of a good thing is usually not good...:)

1. You can wait a week or two before repotting. No rush until you have the right soil mix/pot/etc. ready. Unless it looks like it will die in two weeks then repot immediately.

2. Agreed with Rina. If healthy then you can cut them. If not healthy, then better to get them growing well again before cutting - it will reduce the time it takes for the plant to recover/cuttings to root.

3. Don't pot too big. Every inch in diameter you go bigger in pot, the volume roughly doubles! That means when you water there is double the water available (which can be troublesome for succulents).

4. Maybe a little is okay? Make sure you flush your pots well to avoid excess accumulation of salts. For the garden and outside for sure I have seen works well.