1. IBM is under Lenovo now. if you ever heard before of IBM Thinkpad series, then now it is Lenovo Thinkpad. Actually, all laptop brands are the same. You cant run away from the risk of having a lemon unit, so luck is part of your purchase role. Btw, Acer has started to get better, especially starting from their ivy bridge lineups. So whenever people bullsh*ts about Acer sucks, i would ask them to think before they talk.

2. We dont call it latest processor, we call it latest generation. Now the latest is Haswell, which improves battery life and graphics performance. And FYI, Celeron is enough for office usage and watching HD videos. So to conclude, it wont lags.

3. Yes, but mostly implemented in ultrabooks to keep the slim and lightweight profile.

4. Useless. It is considered as part of a marketing gimmick and as an ad for Windows 8. Constant poking the screen can loosen the hinge and tiring (wont if you are holding the laptop on your lap).

IBM is still IBM (very much alive and kicking)  IBM only sold their laptop business to Lenovo, and Lenovo has been able to leverage technology they bought and implement them across Lenovo models (e.g. keyboard, recovery software ... ).

For your usage, you only need an Intel i3, with Intel IGPU.
Toshiba don't have much choices within your budget.
Much of the lagging that users like you feel is due to:
a. lack of RAM - minimum 4GB in W8.1, 8GB or more is better.
b. slow HDD - go with SSD (solid state drive), 128GB SSD ~ RM300.

Haswell is a generation of CPU, think of it as a manufacturing process. Intel improve the manufacturing process, new generation.
Atom, Celeron, Pentium, Core i3/5/7, are branding. Intel use it to tell buyer what to expect for what price

So we could have Haswell Atom (not yet available), Haswell Celeron, Haswell Pentium, Haswell i3/5/7. (ascending order of power)

What is IX series?

Pentium 2xxxx is Ivy Bridge (1 gen older than Haswell) Pentium.

Anyway, as I mentioned, for your usage, you don't need powerful CPU.

Satellite C40-A103E, Pentium 2020M + Intel HD@RM1449, 2GB, 500GB, W8SL; 2 years local warranty
Satellite C800-1022, Pentium 2020M + Intel HD@Rm1369, 2GB, 500GB, W8SL, 2 years local warranty

Are the re-sellers showing you these Toshiba?
If you could get it ~ RM1.2k, with additional 4GB RAM (RM100) and 128G SSD (RM300), you should be good to go.

why don't you check with the re-sellers right here at LYN garage sale threads? There are quite a few of them carrying Toshiba
And you don't need additional "hard disc", you want SSD