ISO has the most games available for sure. As some never saw a PSN release. PKG often times uses less space. JB folders can be easier for RTE if you're into that but a few games do not work and require some tweaking to make it work.
Look on the back it will tell you the model. It is either CECH-400X or CECH-420X but no one can tell the exact model with the info you have provided. It is either with EMMC or with a HDD
No you essentially have to build each GXEMU with the revised emulator. Kozzy managed to make more room to add more entries in hopes of building a custom one but It never came into fruition. But it can be done but isn't as easy a soft emu where you can just add this CONFIG
Yep will not allow you to jump that far. Both my BC systems I got in low firmware one on 1.02 and one at 2.80 once you install any firmware from 3.00 to 3.55 you can install directly that way. Check out enabling QA flags and enable System Update Debug. You can then freely change firmware. You...
Last I looked into this was firmware 4.88 and the config files are baked into the GXEMU. Kozarovv did some work a while back to extend the amount of space they can use inside to add more config files buyt for an advanced user for sure. You can read about this here...
Hopefully they can improve this as right now it leaves a lot to be desired but a step in the right direction. Had audio sync issues for just about every game I tried. Sleirsgoevy just made a commit that looks as if FPKG support is coming soon.
Try a SSHD I have had great success with these. The one I have installed on one of my systems has been there for over 6 years and working great. If I could find a 1.75tb SSHD I would in a heartbeat.