yes can, just enter cwm, wipe/factory reset, then flash. when restoring apps with titanium, dun restore system data
its just the theme~ best look at features as everyone is now mostly using jkay mod, the themes are getting universal.

you can use apps+data, just not all apps + system data

5 icons at bottom is because of different launchers or is settings. the original touchwiz is 4 icons at bottom, the modified touchwiz has 5 buttons. The UPSIDE DOWN but BUTTONS still same, is because of the rotation transition effect from galaxy note which is in checkrom v4, it happens, just unlock, rotate it, then it'll be back as usual 

Should work well, as antt00 said, nandroid just in case
zipalign: Most ROMs package the darky zipalign which sadly doesn't work. I've edited the script to properly work.
ram tweaks: Most ROMs use Juwe's RAM tweaks or some other RAM tweak that only tweak the Linux LMK leaving out the Dalvik LMK. This creates a gap between memory released in Dalvik and Linux making memory hard to free. SGSII has more RAM so this isn't apparent. In SGS, having tweaked Dalvik gives a noticeable difference.

SD read ahead: Most ROMs tweak this beyond 1024KB. Most of what we need is only 128 or 256 at max. forum.xda-developers.com/showthread.php?t=1032317

CPU Tweaks: Some tweaks are mostly good actually, but not all are sane. ThunderBolt! edges it a bit more for it to become a bit faster as well as battery saving.

You can read my sig: Android Optimization Tips to know what were my basis for each tweak that I did. Most people just copy paste expecting good things to happen (and some do get lucky).

Hi, anyone here using this phone with Celcom? Which modem is the better one with it? Im currently using KI1 but its kinda flaky.. internet connection would drop every now and then & I need to reboot the phone to get it back! Thanks.