I've recently acquired a Tommybuilt G36K.  I'm new to G36s so I have a bunch of questions.

Would I have any issues attaching an AAC M4-2000 to it?  I heard only flow-through suppressors are supposed to be used but I don't know if that's for all G36s or just the G36C.

Do I need to swap out any parts to for it to run reliably with a suppressor?

Mine came with the AR magwell but I would like to use G36 mags.  What do I need other than the G36 magwell - is it just the paddle, spring and pin?

Is there any reason to go with factory H&K mags over Magpuls?

Does anyone have any feedback on the trigger upgrade from ShootingSight?

You should not have any issues using the M4-2000 on the rifle. Flow thru would be more ideal. I would get a hold of Tommybuilt and ask them if that would void the warranty or damage the receiver using the suppressor. You shouldn't be needing to swap out parts out. Again, I would reach out Tommybuilt for questions. You would just need the G36 magwell to swap. The three things I would say  about factory H&K mags over magpul.  Full transparent mags, built in mag coupler studs, and the original look. There is nothing wrong with the Magpul other than it is a good option for mags availability.

I used a ~2010 production M4-2000 on my HK G36K and didn't have any issues. It functioned flawlessly.

There's a buffer in the backplate assembly, and that's what should exhibit increased wear if the BCG velocity is consistently too high from running a non-flow-through can. I didn't notice anything unusual about my buffer.

I prefer MagPul's G36 mags over HK's. They don't snag on pouches. My old HK mags started cracking near the feed lips, but they were probably made in 2002 or earlier. They just got too brittle.

My G36K is a german parts kit build on a TG36 receiver.  Though I did replace the old style handguard with the newer style (still have both).  I also added the TB paddle that gives you the ability to drop mags using your firing hand finger without repositioning.  



I added a Griffin 15x1 muzzle device to it for my GA suppressor and have had no issues and not seen any mal-effect.



As for the magwell, I opted to use the HK mags, as they work reliably and are fairly inexpensive and accessible.  The AR magwell is expensive and makes mag release a bigger issue given the location of the release.  I do have a few of the Magpul G36 mags, but for some reason, in my G36, they require a really hard hit to get them to fully seat.