diff between ddr3 and dd5 = faster speeds. DDR5 is preferred.
Both of your screens are low resolution, as far as gaming goes. The CPU will bottleneck a very fast card, but not the 2 cards you listed.
You want a nvidia card, but it is my opinion that the nvidia cards in the price segment you are looking at are beaten by the AMD cards at the same point. If you look hard you might find the 7770 card for around $100, otherwise look at the $80-90 7750. Those are both great cards for the price. Personally, I think both those cards represent the best value for lower end cards in the last 5 generations of cards. Its a good time to be cheap.
Toms handles this very issue for us each month by listing "Best Gaming GPU For [Insert Price Bracket Here]".
The bracket you are looking for points to either the AMD Radeon HD 6670 or the AMD Radeon HD 7750. I can personally vouch for the performance per dollar ratio of the 7750. If you can acquire one where you live I recommend going that route.
Last question. Will a GT630 DDR5 cause a bottleneck on my CPU or any other DDR5 for that matter?
Depends on the card, if you buy a GTX-680 of course your CPU will bottleneck it. There are so many DDR5 cards out there. DDR5 itself is not the problem, you just have to check the general performance of the card, DDR5 alone is only one aspect but there are many other factors (bandwidth of the bus, GPU generation and clock speed, etc...). You only need to look at the global performance of a card, not only one aspect. Here is Tom's Hardware Graphics Cards Hierarchy Chart, it might help you compare the performance of different cards if you hesitate between two models:
I don't think there's any physical limitation stopping the card, and have never run into an issue like that in 20 years of PC building/breaking. It's probably just a value they use for the card to run optimally under the OS, I wouldn't worry.