As there is still no compatibility with Hermes, use of react-native-v8 (https://github.com/Kudo/react-native-v8) may be a good alternative. Considering that there is already an implementation for node.js, this could be a viable path.
Realm performs well even on older devices, but in the general context of the project it is important to have a more performance JS engine for rendering. In some cases this can be a negative factor in adopting Realm in a project.

Initial discussion here: https://github.com/realm/realm-js/issues/2875