According to the installation instructions for GE 27" and 30" electric wall ovens, a wall oven may be installed under only "approved" cooktops whose model numbers are listed on a label on the top of the oven. Drawing 2B of the instructions shows the installation under a standard 36" high countertop. That drawing also specifies other required dimensions.

(I picked a wall oven model at random and reviewed the instructions that were linked to its web page. Be sure you review the instructions for the model you're considering.)

I'd not do it with any brand . Post the kitchen layout. I'd find a wall for the wall oven, whose very convenient height will be sacrificed. Or find a wall for a vented range. Both are better function usually leaving more prep on an island free of heat.,

A cooktop on the island is a last resort for me.

This never makes sense to me just get a range with an oven. Wall ovens belong up to make using them more convienent

I’ve done it with ge appliance. Both cooktop and oven. I like the “neat” built in look it has as opposed to an oven range combo. all countertops are regular height. I’ve seen it in many homes in my neighborhood. I would’ve opted for wall oven but couldn’t due to space constraints. I’ve attached a picture it only partially installed sorry

This is an example of form over function completely since the combination of a cooktop with a wall oven installed below completely negates the reason people get wall ovens - i.e. to have an oven at a more ergonomic height. The oven installed below the cooktop is generally even lower than it would be in a regular stove so you are paying more for less functionality.

As others have posted generally having cooking in an island is not considered best kitchen design practice since you wind up with a hood that blocks the space and it also renders the island itself less useful for people sitting and gathering around it since you can't have people proximate to the cooking surface.

How small is your kitchen - I managed to get an ergonomically comfortable side opening wall oven into my the small galley kitchen of my high rise condo. There is storage above and below the oven as well as drawers below the cooktop so I'm not sacrificing storage. It's a bit pricier of course since I also opted for a microwave drawer and the cabinets and appliances are more expensive than if I had just gone with even a high end slide in range. Having seen the ovens installed under cooktops in some of my neighbor's units and how low they were, that installation wasn't even a consideration.

i dont have a problem with an under counter wall oven but i see no reason to slavishly locate it underneath your cooktop. do them in separate spots, then you can have pot storage under your cooktop and prep space (and a landing place for items coming out of the oven) over your oven.

i have a slide in glass top range in my vacation home and yes, it really doesnt look as good as a cooktop. it semi worked for me as you can only see its a range when you are in the kitchen, from the other side it looks like a cooktop only. so i get your point of view completely. just not your need to have them in the same spot.