#1
Is there in Zoom G1X good overdrive or reverb how long reverb? And how many effects can be active at the same time?
#2
total effects at once,hmm lets see
reverb
delay
comp/fx
drive
modulation
drum machine

so 6.
and you can also bypass them all
the delay you mean?
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#3
I'd say it's decent. Might just be me but I don't really like the drives it's got, there are a few cool ones but most of it them are just too messy for my taste. The reverb is fine and you should have no problems finding a setting that suits you.

If you by 'effects' mean only comp. effects, then sadly only one.

You can however combine comp fx with drives, delay, modulation and reverb, and of course a simple EQ. You'll be able to find some combinations that you like.

I'm not an expert on effects systems, but I hope this has been of at least some help.

Good luck!