The YM format does not allow playing several samples at once, so obviously the AT2 YM export won’t.
For now, only the (Z80) included MOD player allows to play samples on all channels. But it’s sample only, no PSG sound.
If you want more than that, you’ll have to make your own player… for now! I didn’t do it because not many people seem interested in mixing PSG and Sample sounds, besides digidrums. And it would be a really platform-dependent code, and would use 100% of the CPU. So unless many people ask me to do it, I probably won’t do it.