I think in a computer DAW there is no reason not to apply parallel fx-especially reverb. That is not to say there isn't an argument for scenarios where you apply the fx individually. Highly amped guitar comes to mind for instance. Many times in the past we applied individual fx simply because we didn't have a high enough track count to do so in parallel on even a 64 channel board. Usually I maxed at 32 sticks in my situation for instance with a couple years at 48. If you start adding up multiple keys, multiple guitars, full horn section and crazy drummers........you get the idea.

The easy answer is, you can do it all. That is if you believe you need to do that. Most of the time, I'll add effects/reverbs/delays/flanging, etc. to individual channels/sources/instruments/voices. If for some particular reason I feel that the orchestra sounds a little dry, I might add a little additional reverb to the overall stereo mix. I don't usually do that with rock 'n roll recordings. Sometimes in jazz, I can create or enhance a better room sound to the overall mix even if I have added some kind of individual effects to individual instruments/tracks. Parallel processing can actually produced some interesting enhancements all by itself. Such as including original signal with processed signal in a certain mix ratio, to taste. Daisychaining certain effects are frequently done. Sometimes you want a flanged reverb that auto pans back and forth in an out of phase blah blah cool slurpin' stuff. A challenge to expertly execute such a audible cosmic Odyssey weather in old-fashioned hardware/analog/digital stuff or ITB with a mouse or an Icon control surface. It's all good.

Now making the decision how to accomplish all of this is where you're going to have to spend a couple of years playing with this stuff. And you're not leaving the table until you're done.

Listen to your mother. Eat your effects portfolio.
Mx. Remy Ann David

I agree with both assessments. A large track count can certainly cause anomolies with the addition of differing types of delays stacked on top of verbs. The chances of getting things to settle together in such a case with the use of a lot of verbs is slim. Soloing up a track and adding a delay or verb can be iffy when its added back to the mix. I will solo simply to check the relative amount an effect is adding to a particular instrument, but will always rely on the way it sits in the mix as to the final decision.

As Remy said, adding verb across the 2-bus is relative to the style, perhaps, certainly not dictated by it, but also not needed in a dense rock mix for the most part. Individual verbs and effects are enough in those cases. In an acoustic or a small combo recording with a lot of air and space, I will add a verb to the room mics to add the ambience that might be lacking at tracking. Sometimes this will dictate an addition to the 2-bus but with a room mic or two where space is the goal, adding to these sources will generally take care of whatever you want in this regard.