I have done some tests to answer your question on 4 different systems, a BC PS3 on OFW, BC PS3 on CFW, a non-BC PS3 on CFW, and a 3000 model slim on HEN. Based on my testing:
- Region locking on PS1 and PS2 discs are still enforced if you are using OFW.
- If you are running CFW, you can play any PS1 disc region free.
- If you are running CFW on a BC PS3, you can play any PS2 disc region free
- If you are on HEN, you can play any PS1 disc region free as well.
- In all CFW and HEN PS3s, you can load backups of PS1 and PS2 through the internal HDD
- Burned DVD or CD copies of PS2 and PS1 games do not work on a PS3
TLDR: BC PS3 with CFW (maybe HEN too?) can play discs from PS2 and PS1 of any region. non-BC PS3 with CFW or HEN can only play discs from PS1 of any region.
I hope this answers your question. No in terms of specifics, CFW PS3s can use PS2 and PS1 ISO & BIN CUE files directly from the HDD to boot backups. HEN PS3s to my knowledge can't play PS2 ISOs directly off of the HDD and will need some sort of extra files or modifications before they work. I haven't done any mods recently so I don't really know the exact process to play PS2 ISOs on a HEN PS3. PS1 BIN CUE files should work just fine on a HEN PS3 HDD with no problems.