I've made oak frames that I put triple gazed units into.
I used these, make fixing the unit very easy and provides an air gap. Wouldn't be so easy in steel as you'd to drill/tap the holes or use self tappers. Basically you stick a sealing strip on the inside edge of the frame and these provide the correct spacing for particular unit widths. They hold the frame tight and you need a tool to get them out which makes them secure. You can then fit the outer bead easily as you don't need to holds the glass
https://www.reddiseals.com/product/easyclip-base-unit-and-clip/
They used to do different sizes but it looks like they only do one now
This is the seal I used
https://www.reddiseals.com/product/flexible-epdm-tape-with-lip/
I used these, make fixing the unit very easy and provides an air gap. Wouldn't be so easy in steel as you'd to drill/tap the holes or use self tappers. Basically you stick a sealing strip on the inside edge of the frame and these provide the correct spacing for particular unit widths. They hold the frame tight and you need a tool to get them out which makes them secure. You can then fit the outer bead easily as you don't need to holds the glass
https://www.reddiseals.com/product/easyclip-base-unit-and-clip/
They used to do different sizes but it looks like they only do one now
This is the seal I used
https://www.reddiseals.com/product/flexible-epdm-tape-with-lip/