My choice would be none and find a spot for the cooktop on an wall where good venting can be done. Downdrafts are never as good as a proper hood.

Your island is too small for ANY cook top. Post the layout.

We have installed an Induction with pop up downdraft in a 24" island. It did necessitate trimming the back side of the face frame about 1/8" where the front of the cooktop met it. But it fits and it works. You did not mention gas or electric, but if you are not familiar with induction, research it before deciding. Does not heat up your kitchen like gas, cleaner to use, easier to clean, more energy efficient, and the fastest cooking available.

It is electric. I left that out

We have a JennAir downdraft that came with the house. I hate it. The only reason we still have it is that if we start messing with the oven, it will be in the context of a full kitchen remodel, and we are not ready to go down that road just yet.

I strongly encourage you to reconsider your options, and not go with a downdraft. There are only two options on the market...the JennAir and the Kitchen Aid. Don’t box yourself in.

I'm going to continue beating a dead horse - NO to downdrafts. Induction or gas, hood 6 inches wider than the cooking unit, vented "up & out" on an exterior wall.

It will work - on the last one we did, the island cabinet was 24", but we extended the backside of the island countertop for seating (a large letter D shape). And with Induction, since the cooktop does not get very hot, the chances of an accident are greatly reduced (some articles will say that Induction does not get hot - it does, but only from the heat of the pan going back into the glass). And as mentioned above, a downdraft does not function anywhere close to the effectiveness of an up-drafting hood, but sometimes you have to go with what you have. The family we installed this for have enjoyed it for about 5 years now - they are passionate about their induction top.

Before deciding, crawl up under your cabinet and measure the space front to back to confirm you have 24". Then take a look at the Electrolux 36" if you want a wider cooktop (if it will fit within the width of your island). Then shop at a competent appliance store and see what pop ups they have that will fit within the total space. Also check amperage requirements on new models and confirm what you have at present. You don't want to exceed the current rating of the breakers and wire in place, as it is no fun to change to a larger wire....best of luck!

Generally, a 36-inch Electrolux/Frigidaire/Kenmore will require a 40 or 50 ampere supply (review the installation guide of any candidate device). This will likely exceed the present range wiring ampacity, but you might get lucky. Also consider voltage drop if the run to the service box is very long; in that case upping the conductor diameter will be helpful. You should have a 200A residential service, at a minimum.

Note that this cooktop feed is separate from that which supplies power to an oven, unless an induction range is purchased, in which case one supply will do for the combination.

Downdrafts are virtually useless, and that's the pop up ones that have a hope of working. Surface mounted downdrafts are completely useless.

Kaseki - we have a 36" Kitchenaid Induction in our showroom that is rated at 30 amps. Induction makes much better use of the electricity. Green - agree that pop ups are nowhere as effective as up drafts - but original poster said they are remodeling, not building new. Budgets can force many decisions....

My former 36-inch Electrolux Icon was rated at 46.8A at 240 Vac. Hence, I supplied a 50-A branch circuit using 6 AWG conductors. My current Frigidaire Gallery is rated at 45.2A at 240 Vac. This newer model may be slightly more efficient because (as I recall) the hobs are asserted to have higher power.

can we have a ductless range hood combined with downdraft?.So that both of them can work together for a claaner kitchen

They can work together for a slightly cleaner kitchen than if they weren't there, but in general serious cooking will generate more CFM of plume than those devices can handle, so there will still be some spillage into the room condensing onto surfaces.

Telescope down drafts are a decent improve over flat ones.