2D scrolling on any reasonable platform should be just a matter of setting the viewport offset in a larger bitmap than can be physically displayed.
Not necessarily. VGA mode 0x13 is just a single screen of chunky pixels, and as you may know some really nice PC platformers use this mode smoothly and without jerkiness. The same goes for the C64. There is only 8-pixel scrolling and a lot of smooth platformers obviously run on this, too. No changing of viewports (well, on the C64 there actually is to some extent but only in terms of screens, not pixels), just copying new data into video RAM. These are both proven "reasonable" platforms for 2D scrolling.
There are a lot of smooth and technically superior platformers on modern PC's too. One problem is that it's hard to do everything in time when there are a bunch of other tasks running on the PC. It's not necessarily a problem if you have a fast enough computer, but since most classic Amiga games don't have to share resources with other tasks, looking at the good old, tightly coded DOS games is a lot more fair.
