Besides the extra juice to run a few more games, the big advantage of a 2+ over a 2 is that 2+ units have the FM Music chip internally. On an MSX2 you will need an FM cart for the huge number of games that use FM (MSX Music)
AFAIK GR8NET is only sold by the guy that makes them via the MSX group on Facebook. There is also Carnivore and a few others. I personally use the older MegaFlashRomSCC+ in conjunction with an SD HDD interface as it suits my uses better.
Metal Gear 1 is the real Metal Gear, much better then the NES version. But Metal Gear 2 is simply amazing. Metal Gear Solid is basically a soft-reboot of Metal Gear 2, new story, location, and names, but about 80% of the stuff that happens in Solid happened in 2.
I ended up pulling the trigger on a Panasonic FS-A1F (MSX2 with floppy drive), there was a nice one in good condition with new belt on ebay for $250 shipped. I know the MSX2+ is way better with the built in FM, but I cheaped out a little to get started lol
I think I’m gonna go with the MegaFlashRom SCC+ 512k RAM, and maybe get one of those FM carts. Atleast I got a floppy drive for when I get some disk games or when I want to easily save game progress to a user disk

First games I’m gonna play are Metal Gear 1 & 2, and SD Snatcher. All 3 of those games have english translations which is awesome