Need advice with analog servodrives

I want to refit cnc machine with analog servodrives (-10 .. +10V analog input and pnp discreat inputs)
I choused such devices of MESA to buy:
7i77 and 5i25.

Mother board has 1pcs of PCIE16x and 2 pcs of PCIE1x free.
Does 5i25 supports PCIE1X if not then PCIE16X?
In the magazine:
1) What does mean "PCI/PCIe mounting bracket type - (REQUIRED OPTION: SELECT TYPE)"
- Standard profile
- Low profile?

Machine has no gears on servodrives. It's very fast.
I think it will work maximum on 1,5V of task voltage to reach needed speed.
I know that analog drives works bed at low speeds.
How to increese precision of coordinates movement at low speeds?
I think that to set gears 1:15 is best but expensive idea, I will not chouse it.
If I set between servodrive and control board operational aplifier to reduce working load for example, I change 10V to 2V. Will it be better?
Or is it possible to use 5i25 not with 10V but with other voltage?

Thanks for that, Tommylight.

And what about precision of low speed motion?
How do you think, it will work fine for carving relief, for example?

OK, thanks. I will try standart wiring.