Gtx 750m(gddr5) vs gt 840m vs gtx 850m(gddr3/5)

So I'm trying to do my research and I'd like to know your opinions on these 4 graphics cards.
Obviously in an ideal world I'd pick the best, but I'd like to know which one is best value for money at the moment, and where the most significant differences are and whether they justify a price increase.

1. Would the 750M (GDDR5) beat the 840M by virtue of being GDDR5? I heard 750M runs significantly hotter.
2. Is there a significant difference between 840M and 850M(GDDR3)?
3. Is the price gap/finding a laptop with 850M(GDDR5) justified by the performance increase compared to the 750M/840M/850M(GDDR5), i understand this is the best graphics card listed here but i want to know whether the difference is significant.
4. I have also seen the GTX 765 (GDDR5), anyone able to tell me much about it?

I don't know whether this is the right place to ask, but i'd also like to know a bit more about the CPU/GPU bottleneck issue. Would an i5-4200M suffice for the above laptops? I have the option of 4210M too, I do not know whether this is significant or not, what does the 10 mean?
If someone could suggest a processor/range of processors that would sufficiently match the above listed GPUs

Hope you guys can help, I've done a bit of my own research, I am hoping you guys can consolidate/2nd opinion what I have found so far.
Feel free to suggest to me better alternatives too! THANKS IN ADVANCE!

 

The GTX 850M is a stellar graphics card: NVIDIA GeForce GTX 850M - NotebookCheck.net Tech

According to the same website, the GT 840M is slightly behind the DDR3 GT 750M, so the GDDR5 750M will be better - but not nearly as power efficient. The GTX 850M is about equivalent to the GTX 765M, but I'm not sure if that's the DDR3 or GDDR5 version - and once again consumes much less power.

GTX 850Ms are hard to find, because most manufacturers apparently go straight from the 840M to the 860M, which is 11% better than the 850M in some benchmarks.

 

Ah thanks for your insight. So GT 840M is only a choice if I want a cooler laptop?
I looked up the 765M on the website and it is close to the 850M GDDR3, (the GDDR5 version is better than 765M in every aspect except cost), it would be cheaper, but it is SO MUCH hotter.. Personally, would you be worried about a 70 TDP gpu in a laptop?
Also, would an i5-4200M with these graphics cards be advisable? Would picking up the 850M GDDR5 be wasted with that processor?

Yeah, I've found that too... the price difference is kind of too much for 860M... Thanks nonetheless

 

The DDR3 850m is the one that is equivalent to the 765m, the gddr5 is like a 770m, but the only laptops that have the gddr5 version of the 850m are the MSI GE60/70 2PC if i am not wrong

 

The maxwell 860M is little below the 770MGTX. The 850M is more around 675MX levels.

Yes if you OC them (if they are GDDR5) you will see decent performance. Steer clear of any ddr3/gddr3 card it will bottleneck the performance. Unless you intend to game at 1024x768.