Welcome to TFF.
Starting with your last question/issue...if the plants came from tanks with fish, it is generally advisable to quarantine them the same as you should do for fish, for a week or so in the case of plants. This can help to ensure they are not carrying fish problems. But this QT should be in a tank or other container of water the same as your aquarium water (GH, pH, temp) and obviously with a light. But I have many times not done this myself, and added new plants to the intended tank.
Snails are not a problem, and if any arrive, consider yourself fortunate. The small snails like pond, bladder or Malaysian Livebearing do not eat plants (they will eat dead and decaying plant matter) and they are beneficial to the biological system.
Java Fern, Anubias and java moss are basically low to moderate light requiring plants. That means they are less fussy with light and their nutrient needs are lower because of their slower growth. However, they can develop algae like black beard/brush under direct light, so floating plants are always advisable over them. A comprehensive (complete) liquid plant fertilizer may be helpful, depending upon your fish load and light.
As you mention, Anubias and Java Fern grow attached to wood or rock. Make sure the rhizome (the thick "root" from which leaves and finer roots grow out) is not buried or it may rot and kill the plant. If the fine hair roots do work their way down into the substrate, fine, but let them do it on their own. Just ensure the rhizome is above the substrate.
