A good/typical msx2 model here in NL is a philips 8250, but I dunno how those are spread across the world

A typical MSX2 has *at least* 128k memory (128k ram and 128k vram)
important cartridges: fm-pac, at least one Konami SCC cartridge (preferably with a switch) if you want to play disk-versions of Konami-games with SCC music.
A music module was an essential in the 90's .. now anno 2005 it's a bit over I think ..
A Moonsound with 640k mem is nice, and after a long time, Sunrise sells them again! (www.msx.ch)
A Compact-Flash interface, or an IDE interface with a harddisk, is very comfortable these days..
difference 2/2+ .. msx2 has max 256 fixed colors in screen 8, or 16 from a palette of 512 in other screens. msx2+ has way more colors (up to 19268) tho it's a bit more tricky to draw for those screens due technical limitations (YJK system). Looking back on the past msx history, the MSX2+ screens weren't highly popular for games.. except some titlepages here and there. That's mainly because you've only 2 pages, and vram copying takes twice as long, because the format is simply twice as big compared to (the more popular) screen 5 on MSX2.
Technically there are more differences with the MSX2+ .. but that's nickpicky stuff no-one cares about
the cable-thing: dunno
