Well, you just have to experiment. ROM cooking is not by recipe. Just take note of your bootloader version as you WILL have trouble with ROM size and certain bootloaders. Also, try to use XP and Activesync 4.5. I encourage you to read and search, e.g. TouchFLO:
http://forum.ppcgeeks.com/showthread.php?t=11945
You can install any program you want post-flash. Just be careful modding the phone. It is like any computer system...don't challenge the hardware resources.