Lenovo Z50-70: CPU update

[PedroFX]

Good morning
I want to buy a similar laptop to my current Lenovo G50-30.
I mean Lenovo Z50-70, version with 4GB 840M.
Below I am posting screenshots confirming that I am interested in the topic, and I apologize for lack of BIOS, because I do not yet have the planned laptop.
I just have a dilemat. The laptop has an ACLUB motherboard and an i7-4510u processor. However, I would like to use the best processor. I see more efficient Intel processors on the Wikipedia page. Which ones will be compatible after BIOS update? Which one will be the most efficient in combination with this graphics card?
Haswell-H Core i (4th gen) - i7-4600U + HD 4400
Haswell-H Core i (4th gen) - i7-4578U + Iris 5100 (28W)
Broadwell-U Core i (5th gen) - i7-5500U + HD 5500
Broadwell-U Core i (5th gen) - i7-5600U + HD 5500
Broadwell-U Core i (5th gen) - i7-5650U + HD 6000
Broadwell-U Core i (5th gen) - i7-5557U + Iris 6100 (28W)
In this case, I would buy the much cheaper Z50-70 with an i5-4210u processor and max it out for this laptop.
I saw a test of a G50-80 laptop with an i5-5257u processor (28W) and I see that the motherboard supports a processor of this power, but has a worse graphics card. For safety reasons, I would also buy an original Lenovo 90W power supply.

[DeathBringer]

Current CPU is soldered to the motherboard.
There is no way to add support of Broadwell to this BIOS.

[PedroFX]

It's a shame. Will i7-4600U or i7-4558U/i7-4578U (Iris 5100) "Haswell" exceeding model specs be able to run in this laptop?

[DeathBringer]

This motherboard can run with any CPU with Haswell-U or Crystal Well core.
But CPU re-soldering can kill the motherboard.

[PedroFX]

I will compare the i7-4510U to the i7-4600U, although I expect small differences. i7-4558U and i7-4578U will probably be more efficient, but apart from the risk of damaging the motherboard, I am worried about temperatures. I didn't know about Crystal Well before, but 4 core seems great. I will think about it.

Maybe using the G50-80 (different motherboard) with "Broadwell" would give access to better processors, but it has an inefficient Nvidia 820M and an unpredictably efficient Radeon M330.
I think upgrading the graphics to say 840M, 850M or 940MX is much more difficult when choosing compatible parts and BIOS compared to CPU.

Edit: I think about 37W Haswell: i7-4702MQ and i7-4712HQ, i7-4722HQ if it is Crystal Well?

[DeathBringer]

Crystal Well is not suitable for this motherboard.
I'm sorry for this mistake.
P.S. i7-4702MQ, i7-4712HQ and i7-4722HQ are Haswell-H, not Crystal Well
But you need Haswell-U only.

[PedroFX]

Thank you for your answers. It helped me a lot understand the issue. If I replace the CPU, I will let you know. If I have additional questions, I will ask them. Regards