Yes for that benchmark I am with 5% BIOS OC (everything maxed out), all four cores are at 3.9Ghz because this test doesn't push the cpu that hard, it is more memory depended, so if you can increase the BLCK more instead of the multipliers you can get a much better score.
About different multipliers among cores, you can enable EIST and C1E from within ThrottleStop and you will see them fluctuating according to the workload all the way up to the multiplier you set as maximum. If you have them disabled you will have the same fixed multipliers across all cores. I don't think you will be able to reproduce the TurboBoost function with higher multipliers than the default ones, plus for me the 940XM never had that behavior(TurboBoost as described by Intel), with or without any tweaks and I think that has to do with the BIOS from Dell.
About the GPU and the registry changes, you don't need them if you plan to flash the GPU from DOS, the registry mod is only needed when you are planning to use programs like riva-tuner to change the clocks from within Windows, I personally avoid them and I don't mind flashing the card every time I want to change the clocks, it's a 40sec procedure for me anyways. You can try with 1.1V and find the clocks that are stable for you, I could even hit 870+ with the stock 1.05V.