You might think roots are just roots, but there are actually different types of roots. Understanding the differences could help you when transferring plants from one substrate to another.
Water Roots
Water roots grow when your plant is in water or in a substrate like leca. These roots are fragile and must be handled very gently. They grow so that the plant can collect water without drowning from the lack of oxygen.
If you transfer your plants from soil to water, the roots that were on your plant may entirely die off, since they are not prepared to be constantly submerged in water. This may set your plant back in its growth as it will need to quickly put more energy into growing brand new water roots. If this happens, you will want to be sure to remove those soil roots as they rot away, otherwise they will make the water stink and could cause other problems.
Water roots grow more quickly than soil roots. This can be helpful when acclimating plants that are arriving from a completely different environment. For example, when plants arrive to me from places like Ecuador, they arrive bare root, and to start acclimating, I plop them in a vase or bucket of water. Since water roots grow quickly, it helps the plant get the water it needs as it's also acclimating from a more humid environment to a less humid environment, as well as healing from the shipping process.
The easiest substrates to transfer plants to when they are in water would be leca or other similar substrates.
Soil Roots
Soil provides more nutrients for plants to grow bigger and stronger than when in just water.
Soil roots are thicker and more sturdy than water roots. They're good at capturing nutrients that are in the soil and require some level of oxygen to function. As mentioned earlier, if transferred to water, these roots will start to die off, since they don't like to be completely submerged in water.
Likewise, when plants are grown in water and transferred to soil, the water roots will start to die off and the plant will have to quickly put energy into making soil roots. This is because the roots are used to having constant access to water. Most soil mixes are created in order for them to dry out, since soil roots require some oxygen to grow, so it is a tough transition for the plant to make.
The easiest substrate to transfer plants to when they are in soil would be sphagnum moss as plants grow soil roots when in moss.