For international flying there’s a magic number: 22. Pounds that is; or 10 if you count in kilograms. That’s the most common carryon weight limit for international carriers. Some, like the smaller (mostly British) airlines have even lower limits, but 22 is the mark to shoot for. To be on the safe side make sure that your “personal item” is included in this weight and that it fits inside the larger carryon, since some countries - most notably the UK - allow no additional personal item unless it will fit in one larger bag. The dimensional limits have not changed: 45” combined still works almost everywhere, some allow a bag up to about 50”.
If you’re committed never to check a bag it’s never been tougher. But, given the mounds of checked luggage (and 1000’s of pieces lost every day) the rewards of going one-bag/carry-on have never been greater.
This link has information on international luggage limits for various airines. It’s not 100 percent accurate (it assumes you usually are allowed the extra personal item, which is no longer always the case). Always check the website of your airline. Some carriers allow fudging, but the safest bet is to assume they will follow their own rules when it favors them.