Bravo for taking the first step to becoming a bonsai-phile!
Both of your choices should be very good trees to start out with - easy to care for and relatively easy to shape. (Both are easy to propagate into more trees as well.)
I do have two concerns to point out:
1) With them potted in those plastic trays, there doesn't look to be any drainage out the bottom. This might be tolerated by the Schefflera, but plants in general don't care for "wet feet" all the time. It can lead to root rot.
2) These two plants have very different moisture requirements, which concerns me since it looks as if you have potted them together.
Schefflera like lots of moisture and Portulacaria prefer to go a week or two between watering and to almost completely dry up.
This specifically pertains to the Jade Tree and not the Baby Jade, but care is essentially the same:
"Due to their arid natural habitat, Jade Trees are capable of holding large quantities of water in their leaves. Over watered specimen develop poor root systems which become incapable of physically supporting their heavy foliage and become top heavy. Unlike other bonsai species, Jade should be lightly watered, if the compost is allowed to dry in-between waterings the roots are encouraged to search for moisture creating a far stronger and vigorous root system. This also reduces the store of water in the foliage reducing the tendency to be top-heavy. Water is only essential to the plant when the leaves start to develop a wrinkled texture. In winter this can mean watering as little as once every 2-3 weeks."
https://www.bonsaihunk.us/info/ScheffleraBonsai.html
https://www.bonsaigardener.org/hawaiian-ubrella-bonsai.html
https://www.bonsai-bci.com/species/portulacaria.html
https://www.bbg.org/gar2/topics/plants/2002wi_bonsai.html
Hope this helps!
