Pluggo in Max 4

i am still using and building those, too.

a)
it is both. same plug-ins and same runtime installer, but works as AU/VST/RTAS.

b)
not directly. but using [plugsend~], a plug-in replacement for [send~], you can send audio from one plug-in to another.

c)
actually i cant rememerb how that worked, i think in maxmsp v 460 you shoould actually be able to open them with the vst~ object.

but why do you want to do this?

for testing audio and messages, parameters and programs, you can do that just fine with the uncompiled plug-in patch.

otoh, for testing complicated GUI stuff, parameter automation or inter-plug-in audio communication such as required for your sidechain, you should really test this in the host program where you need it to work later.
these things can be host program dependent, and stuff eventually works differently from program to program.

p.s. sending audio between plug-ins is not easy. logic audio 5-6 for example might totally freak out when pluggo is trying to do that. other programs might cripple the buffer between plug-ins when you jump in the song position. it generally works, but handle with care and dont expect someone helping you.

with everything else i will be glad to help. ;)

-110