Nice.
Are those photo after the repotting? If yes, you did a nice job.
Potentilla - I would have planted it just a little bit deeper. Exposing the roots too early on a young plant will actually delay the development of the nebari.
First branch is too long and straight. I would use wire to bring it outwards, and put a little bend in it. Otherwise a very nice start.. Do your next pruning after the summer solstice. When you want flowers, for that year, you let the potentilla grow without pruning. Flowers come on the current year's growth. Nice.
Chinese elm - The branch coming from underneath the trunk is awkward looking. It is filling a void, I can see why you keep it. But it is not attractive. Elms grow rapidly. & back bud profusely. I would allow this tree to grow. until after the summer solstice. Then I would remove the branch originating from underneath. The elm will create buds all over the trunk. Let the majority grow out for a season, see if any are better placed to become replacements for the awkward branch. Or you can just let the elm grow without any pruning this spring and summer, and see what buds have sprouted when you look at the tree in autumn.
Metasequoia.
I love this species as it is very cold tolerant. My climate is quite a bit colder than yours and I leave my Metasequoia outside, only shelter is protection from wind. this winter we had several nights where temperatures dropped to -25 C, with a one night to -31 C. (-23 F). The pot was set on the ground under the bench it normally grows on. Buds are starting to swell, a little green showing right on time as if it was a gentle winter. Very hardy.
It is a very rapidly growing tree. It will be difficult to keep as a small size bonsai. They are easier to keep as a larger bonsai 0.5 meters and larger. Best ones I've seen are about 1 meter tall. But if you can keep it under control, wonderful.
The very first branch is vertical and arrow straight. I would cut it off now, not flush, but above the collar of swollen bark at the base of the branch. There are many dormant buds in the collar. One or more bud will sprout, and likely it will not be straight vertical. The two branches at the apex are too long, I would reduce their length by half. Take off those three branches, keep it well watered. And by a week or two after the summer solstice this tree should have many more branches than it does now. Prune it again about 2-3 weeks after summer solstice. If it grows rapidly prune again 8 weeks later.
Metasequoia need a lot of water. It will do well if you place the pot in a tray of water for the 3 hottest months of the year. Make sure it does not approach dryness. They are heavy feeders also. Have fun with this very rapidly growing deciduous member of the redwood family.
