Your new computer probably has CPU throttling.
Turn that off when working on multi-media.
Similar problems:
+https://forum.renoise.com/t/solved-big-performance-problem/25511
That was most likely it! The song with the supposedly “crappy” plugins runs at about 50% CPU usage and eventually flips over, so that didn’t help much here, but the other songs are now more in line.
Thank you!