The Vet just being cautious, whenever you are at home, you can let him run free as you are around to keep an eye out for the operation wound.. whenever you not around can keep him in the cage so that he don't hurt himself.. that I believe is the Vet intention...

As for me I keep the cage around with the Door open. its a 2 level cage. I kept one of the litter box inside bottom level and also the drinking bowl on 1st level. The cage got an extra bottom layer so in case spill water easier to clean. What my cat will do is that she will jump from the table to the top of this cage nowadays.. Her kibble is also hang outside the cage side and so she quite comfortable with it.. Its more like her playpen... No need to lock up already....
At night she sometime sleep with us on our bed... She got the whole house for her to sleep sometime on sofa, sometime on our lazy chair, sometime on our ironing board.. she got her own bed.. but that is the last place she sleep at......

For me I prefer the Feather at the end of a stick teaser... You need to make sure its a real feather... the cat will go crazy.. can always get another real feather from those specialty stationery shop once the current one get torn to shred....

If the ear are clipped or tipped it means been spayed/neutered. If have collar then maybe owned and partial outdoor cat. This type of cat know how to return home for meal.
If you want to take home, just bring a carrier. as seem easy approachable think no issue put into a carrier and bring home...
If a community cat, who don't want a proper home to be taken care and pampered. If no collar, think its save to take home...
Best also leave a message at the shop you have taken the cat home and if the owner came looking can contact you.

1) Which litter sand type is good? I read that there's tofu and all so what do you guys use? I stay in a condo and would like to have as minimal smell as possible.

Using Clay Litter, Do note that clay litter go by Kg and if condo a 12Kg packet not easy to carry. If buy in Bulk say 5 bags of 12Kg will really be a task to carry. I am using OdourLock and seem to does that, lock the odour. Only release smell when scooping and if the cats don't properly buried it. If money no object can always get those automated Litter box that is enclosed. No scooping needed and just bag up and throw.

2) I am planning to go with dry food ( kibbles ) as much as I can. In terms of general health, any supplements that I should add in? I also read that it's good for them to consume raw food. Am thinking that I can get some raw salmon for cheaps so if it's good for the cat, why not?

Mine free feeding kibble and water in tray and fountain. I let them run free at my Condo. Feeding them those 80gm can. Will mix those 80gm can when buy. So they can have variety. Not buying same flavor only. Mix brand as well for variety. Kibble currently using Leornado. Last time using Blackwood. If money no object.. then Orijen....
Food is always the issue.. 1 of my cat is a fussy eater but luckily I have another that eat everything. So the fussy one if don't eat I just pass to the other.

3) How often do they really scratch? I have things on the ground that I really don't want it to be scratched as it's expensive so am trying to figure out how to avoid it.........

Part and parcel of having cat... they need to scratch. For me I live with it. Have all the scratching post and stuff. Cats can be mischievous so need to scold a bit. I don't mind some stuff being destroyed by them, also get those suppose to be cat proof...

4) Vaccine, what is compulsory? How often to deflea/deworm?

Refer to your Vet. Mine all indoor so very little issue with Flea and worms...

<Lucky I have a storeroom at the basement so I can store it downstairs first but I agree with you on the weight being a bitch. LOL, how much are the automated litter box?>

I purchase in bulk as sand/clay can keep well.... Just carry once few bags with trolley every few month. Automated Litter box, there quite a few selection, manual one cheaper.. think RM200-300. Those electricity driven one are more expensive.. range from RM500 think to a few thousand depends on how complicated... Expensive type... after every bowel movement it will clean.. to empty you just press a button and just pick up the bag.. of course you pay for the convenience... but you still need to fill up litter and throw away the poo.

<I was shocked at the price of Orijen but getting 5.4Kg seems to be more worthwhile and assuming the cat eats about 80g a day, it can last for 2 months which is okie I guess.>

To me I don't really recommend Orijen, in case your cat get fussy.. end up don't want to eat other cheaper alternative....

<Will prolly get a scratching pad or post. I have floorstanding speakers which I don't know how to scratch proof it. lol. My sofa is about destroyed anyway so they can do what they want with the sofa>

So far my Speaker still save from my cats... Maybe they don't like KEF..... one of it just love to sleep on my centre speaker.... Sometime on my AVR. Don't know how she tolerate the heat.... AVR run hot. Good luck on Speaker.. some of my friends cats love the play with the speaker cover, mine don't.. lucky me....

To me get them spay/neuter on the soonest... so less worries.... once done vaccine.. and vet say can.. just do it

You can check out my HT system in my signature... just a small system for Home use....

Yeap, Odorlock is on the expensive side of clay litter compared to China stuff. Think 6Kg less than RM50 and 12kg should be less than RM100. Just see how you manage the weight.
As in normal clay type.. sure got spill and stuff. So need to sweep.. Dust so far quite manageable. Clay litter these 2 are the main con... Dust and spill.