ton, there is no 20T cog on a 9spd MTB cassette. Well none of mine anyway. There’s 24/21/18 though.
22/24 is a bit easier than your 32/32, 22/21 the tiniest fraction harder (though you’d not notice), and obviously 22/18 a bit harder still.
You’re better off knocking the front mech into the granny ring earlier on on a climb, and using more cogs further down the cassette whilst the climb is easier. Then as it toughens, knock it up one cog at a time on the back. This is a far better option than keeping on mashing 32/32 as it gives you more bail out options, cos as everyone knows front mechs don’t like shifting down to the granny ring very much when under load.
I’m with GW, good that Shimano finally start making sensibly ratioed twin ring setups (22/32 is IMO not enough spread). The 24/36 I used to run for a while was superb, the biggest problem was the raceface BB was absolute shite, and I couldn’t wait to get rid so I could use Shimano HT2 cranks.