You can use any cfw really, you need popsloader though, it's a plugin - it lets you choose what fw ver. to boot the game in basically as some games have better compatibility with different versions, youtube for vids on how to use etc - it's simple.
For multi-disc eboot's I reccomend PSX2PSP 1.4.2 and single disc games Simple Popstation GUI 3.00, they are the best at what they do.
Some, very few really, games require using different ID's when making the eboot, it's easy as changing 4 letters and 5 numbers in a blatant option when making the eboot. For each game you convert you should chek this url:
PSX on PSP Compatibility List - TheGamersPress
it will let you know the best pops to load a game with or if the game needs a different ID or anything.
also if you wanted to use a game with content ripped to save space then you can still do that, or you can convert games with patches applied, like translations (like tales of phantasia, Dracula X, etc) or game fixes (ff7's spirit bug fix comes to mind) then they will still work perfectly when converted.
Also it's worth noting that NTSC-U games have better compatibility than PAL and PAL games may have border/screen size issues.
also you can access manuals or walkthroughs anytime during play if you press home and then choose software manual, first you have to convert those to document.dat format and put that in with your eboot.pbp, get some ready made walkthroughs here:
Alphabetical List of All 101 Walkthroughs, Guides, Maps, Etc. (most from Casper88 )