What modern wheel and tire size could be replaced from 32-630 ( 27 x 1 ¼ ) wheels Referring from the question, specifically, what is the closest modern wheel size for my old 32-630 ( 27 x 1 ¼ ) wheels. It's hard to find rims and tires for that size now a days. I'm looking for the closest size in terms of wheel diameter. It should not go any bigger but close to exact size or smaller.
I'm also converting my bike with disc brake, so rim size won't be any issue with rim brakes.

I have read this guide and mostly I found closest to mine is the 700C or 622mm ISO version for road bikes.

https://bike.bikegremlin.com/285/bicycle-tyre-dimensions/
After measuring the outside diameter of my ETRTO 630 sized rim and tire with a modern ETRTO-622 sized tyre, (ie a "700c") I notice they have a slight difference which my fork and frame can tolerate.  

The 622 rim is 8 mm smaller diameter (4mm smaller radius) than a 630 rim and is a good fit.   So therefore I will go with a more modern 700c wheelset.

Thank you for those who have comment and helped me decide better.