Outside of the official LiteOn settings (which you already know about – HyperTuning, OverSpeed, etc), there isn’t anything to really tweak. Much like the A1 and A4 drives of old, the iHASx24 drives flick HT/OHT on automatically whenever the write strategy for a given MID demands it.
There is no custom firmware to unlock higher over speed support for more discs, but the drive should be slightly more stable at high-speed writing (the first 18x and 20x drives would sometimes refuse to slow down when they were struggling to keep up that high speed), but I think the drives are also more likely to refuse to burn at a higher speed if the discs aren’t good enough.
There is no way to achieve an RPC1 drive if the old tools don’t work; I am not sure if any of the tools can reset the RPC2 setting. If none of the tools properly support resetting the drive’s region setting, we generally recommend using something like AnyDVD to bypass region locks.