In my studio, with newly upgraded acoustics, I have a vocal area specially tailored to give me a
sort of tunable room sound. Then I follow that up with my favorite vocal verb, Lexicon PCM Vintage Plate,
with an eq for further shaping on the send.
Most of the time, you can get away with using very short delays instead of reverb, so research using delay
instead of reverb.
To give you an idea, just one of the many considerations when choosing reverb,,,,
Regarding reverb, though all parameters are important, your predelay can have a great impact on the sound.
For sounds I want farther away, I use little to no predelay, for upfront sounds, I use longer predelays timed
to the tempo of the song.
Ahh, hell, the other parameters are just as important.
Then you have reverb damping time of frequencies, ect..ect..
Some reverbs have a type of Through mode that requires you to engage the direct sound
if using directly on the track(
Waves Trueverb)
There is no rule, unfortunately.
Read books like "Mixing Audio: Concepts, Practices and Tools", and others like it.