Ikea kitcab (metod) should fall under mid-tier.
It is not the cheapest outfit, but for a midtier solution the value you get from it is pretty good (fully featured 8ft for <7k all in) without having to pay 20-30k for a 8ft kitchen.
Depending on what are the nice-to-haves and must-haves the price variation between options can save a few hundred bucks.
e.g. basic door 20/30, fancier handleless door 100+
e.g. basic sink 265, fancier sinks can be 570-1200

Comparing 8ft size kitcab works below for a feel of what my neighbours also signed up for:

0. Cheapest bargain basement 2400-3000
1. 4800 for unprofessional vendor
2. About low 5k; adjusted based on pfr cost to 8ft (/9.5*8)
3. My own self-installed Ikea kitcab 6100 (full bottom drawers, w/ tap and fancy sink, without the ikea lighting option)
At the other end of the spectrum will be Signature Kitchen which will probably be in the ballpark of 25-30k for a 8ft kitchen.
This is considered expensive in Msian context  - for a feel of the price range you can skim through https://forum.lowyat.net/topic/2663554/all

Design either you can DIY using the tool online at yr convenience, or book a slot to plan plan at nearest store.
Important part is you have the measurements of your kitchen.
Last time they can also do onsite, but now with pandemic I think lesser contact is safer.

The basic concept is quite easy, pick carcass frame size, add shelves/drawers, lastly pick the doors/drawer fronts and soft close stuffs for hinges/drawer rail. Basic type need handle, for handleless type it cost more but its a personal preference as I hate the handles catching on me.

Parts list autogenerated by the design tool. Save the design, order at the store without appt if u already sure thats what u need. Just go there and tell them "I want to open SO please" just login your design there, auto pull based on the design ID#, they give a onceover w.r.t the nos. of legs u need and to confirm your fittings (basically small stuff). Then once SO created just pay at counter and collect the goods.

Between Ikea Cheras and Dsara both are generally positive experience however if high demand parts u may need to buy n collect from another store. Last time I bought whole bottom half all in stock at Dsara, then want to add the top half ended up piecemeal from both central stores, so happen everyone also installing the same look so low parts, need to visit the other store and online ordered the door which came from Batu Kawan PG.

Installation either DIY or book their installer also can.
Its certainly DIYable, alot of online videos and guides, some tools required here and there.

Looks like existing sink will be smaller and D shaped..the ikea sink is actually more squarish so it will avoid gap. The base cabinet CAN-use lah with existing sink but there will be a funny gap ya. Check pipe runs in X Y axis from the water point and drain point so the planned drill holes do not clash with the pipe runs.

Option one confirm fit well.

Custom made can be variable quality as its not that "easy" to trace the outline of a 3D curved object like the existing sink to do rounded cuts.