If i use the 5 Mbps package, what is the real download speed i can get?

550-600KB/s range probably

That is enough for me.

If there're high takeup in your area rarely you will get even close to that with international sites.

It won't be much difference between a 4mbps, a 20mbps, 50mbps or a 100mbps line.
Save your money for other things.

A stable and dependable line is more of your interest.

My friends from Japan, US, Taiwan, HK and even Singapore often tells me that they are more than contented with their isps entry level packages which starts around that kind of speed.

for people getting unifi package do they still need to keep the homeline (copper) if they have one?
is unifi package come with a phone number?

So, between the HSBB 5 Mbps and the 4 Mbps package, which is more worth it?

4mbps streamyx, since there do not have any monthly bandwidth cap issue.

HSBB 5mbps "have this no cap" "FOR NOW" thing. That means they can easily cap it in the future. Unless they agree on signing a 2 year contract with NO CAPPING or Reasonable cap bandwidth that most agree on. Dont bother signing up. Promise from word from the Tm CEO alone cannot be trusted, trust ur signed agreement. Black & white sign only talk else ask them fly kite.

If i subscribe for the 5 mbps package with a 2 year contract, the monthly fee is still RM149?

4mb-5mbps is more than good enough actually.

I've discussed this before. Unless you rely very much on in house servers which resides on the isp's own datacentres your international site surfing is limited to around that speed even at the most off peak hours.This comes from my experience of using many fiber and cable connections around the world.

Unless you live in a country where they mostly surf their native language and surf during off peak hours, rarely you can achieve high speeds with international connectivity.That is also because they are unused.

Once the foreigner population increases in a particular area, the international bandwidth which they have will quickly be used up resulting in the same slow effect. There's no free food.

I've tried doing speedtests from many countries like Europe, US, Japan, Taiwan, Singapore and Australia. 
The people there told me don't waste your time getting anything over 10mbps because you'll rarely achieve such speeds if you're the typical internet user. So you might as well save up the extra money because it's like when you go for a buffet meal and the organizer pretty much know how much a regular can eat.

If some alternative isp is able to provide 4-6mbps average access speed in my area, I'll gladly take it up even if it were to cost similarly to Unifi VIP5 even if it's slighly slower by 1-2mbps.

Have you all heard that Starhub's 100mbps DOCSIS 3 cable modem service is not getting enough responses?Many think it's a waste of money unless you share your home with many tenants.

for people getting unifi package do they still need to keep the homeline (copper) if they have one?
is unifi package come with a phone number?

That u have to read the contract urself. I seriously do not recommend getting HSBB until they have proper draft in the bandwidth cap issue in 2year contract agreement where it is reasonable.

60GB per month is NOT enough even for simple youtubing. It should be 5 times of that, say 300GB.

What will happen if i over the quota limit?