I have plugins that are only available under VST2, or the update to VST3 involves additional costs. Is there a way to load them into SoundManager VST Host anyway?

SoundManager does not load VST2 plugins directly. However, you can try loading your VST2 plugins into a VST3 container plugin and then integrating that container plugin into SoundManager. For example, you can use Native Instruments’ VST3 Komplete Kontrol plugin as a container, since it can still host VST2 plugins.