hmm
hmm
Also Sonic on the Mega Drive had multiple framerate drops, e. g. when you lose lots of rings.
Dreamcast would probably work, given enough effort by people who know the platform inside and out. But then, a much lower barrier to entry is probably a significant reason as to why Sega was willing to fund another 2D Sonic game in the first place.
There really is no excuse whatsoever for a 2D game like sonic mania to run badly on even low-end PC hardware even with built-in graphics hardware.
Memory bandwidth is the main concern when blitting several layers of pixels 1:1, unless you have some kind of crafty system in place for avoiding overdraw. Although Sonic Mania seems to genuinely use a 320x240-ish internal framebuffer, so my wild guess is that the bottlenecks relate to scaling and post-processing, or possibly some funky driver use causing sync issues.