Yes of course you can only play japanese games online with a japanese ps2. And yes .30 is much better then .20. Also if you get a v0 scph-10000, 15000, or 18000, when you don't want to boot the HDD you can simply remove the memory card with the HDD drivers and boot the ps2. Then if you want to have the HDD, boot the ps2 with the DMS in sleep mode.
JAP 60GB PS3 (release date)
37000 L V7 Ocean Blue Matrix Infinity BB Navi (.32)
30001-R V4R Magic ICE 91f3+ PS2 Linux (2.4.1)
10000 V0 No Mod, PSP-1000 1.0 FW 100K release model
PS2 Linux Kit (BB Navigator Installed)
Scph-5501 Stealth, All Sega Systems
Cube with Save, Xbox 1.0 Modded