The Klanghelm meters are excellent and cheap. Also they are very close to the ballistic of real VU's which I also have. (not all are!)
You can treat digital the same way as analog. All you do is choose a reference level. LIke
Bat for example -18 dB rms = 0 dB VU. In my case I work at multiple ref levels (as per K system) but usually only two though. -14 dB rms = 0 dB VU or -20 dB rms = 0 dB VU.
You set that up on the VU meter itself. You need some sinewave alignment tones also.
Once you do this you can treat your digital system exactly like analog. All you do you is adjust your VU's to give you a reading of 0 dB VU everywhere in your mix starting with the tracks themselves. In and out of plugins and on your buses too and the masterbuss of course. But you actually have 14, 18 or 20 dB of headroom sitting above to catch those peaks.
So you watch your rms levels and don't sweat the peaks at all. They just take care of themselves just like they did in the old days. I never see a clip light come on anywhere in a mix. If you do you are doing something wrong.
Many VST's vary wildly in their rms levels. If you adjust the output of any VST's before bouncing etc so they just peak 0dB VU you won't have to fiddle with them from that point on again.
Plus every mix you do is at the same rms level. Makes mastering much easier too.
Fast sounds such as drum sounds are a little different though. They have high peak values and very low rms values usually and the VU takes 300 ms to reach 0 dB VU so they won't show those sounds very well. Peak metering comes into its own then. Once you send all the drums to a drum buss though you will have enough rms level to move a VU more normally then.