I didn’t use them but did get a quotation from them on cabinet work. To me they are ok from quality standpoint but price is on the high side compared to others unless you are competing with Signature Kitchen.

China quartz can be cheap RM100+ per ft run. Silestone can range from 350-900 per ft run. There are even more expensive ones around. Blum hinges are expensive. Some can cost 700 per set. But they last forever. My current kitchen are full Blum and Silestone and those are the killers. There are cheaper alternatives but you should get your supplier list all the components used.

You meant Hefele? Then it is ok. Not bad not Blum but good.
Counter top you just have to ask the supplier. Some Silestone has logo but mine doesn't but they are genuine. The difference between good and not so good quartz is the bonding resin  used. Silestone is more than 90% quartz and has anti bacterial material added. So it is safe to prepare food directly on top if you so desired and also tough like hell. But you really can't tell easily until you use it.

NP. Just ask your supplier what's the brand of the quartz. Generally if they don't tell you then it is general china made one. Those I doubt they have specs provided.

The higher the % of quartz the harder the counter top but like I said the bonding resin is quite important. Mine I can put hot pot on top and still no problem. You don't want to risk those china made quartz with unknown specs. That said if you use it carefully even china quartz will last you a long time. Just don't select those white ones because cheaper brands white color can be easier to stain ... even for quartz due to poor bonding resin

Tell me which self respected manufacturers will say their products are non premium. It is premium of he can tell you his quartz content is >90%. And the type of bonding resin/glue used. That said even 75% quartz content is decent enough but you need to exercise care when use.

It is still harder and easier to maintain than marble and some natural stones, solid surfaces or woods.

If you were renting it out even melamine is ok. Tiles are cheaper too. We are talking about own stay. Not all are made in China. Granted some in China are good too but Silestones are from Spain; Ceasarstones are from Israel/USA. Just like some cars are not made in China but in Germany 🤣