I have some i23s and have used them with a variety of tyres.
Generally speaking for lightweight easy-rolling feeble-sidewall pressure-dependant kind of tyres e.g. Ardent/Nobby Nic 2.25/2.3 tends to be the sweet spot but (on the front) I’ve used 2.5 Minions and 2.4 Shortys. Obv both of these are narrower than stated but Shorty has a slight advantage over the Minion insasmuch the shoulder lugs are more forgiving and tend to absorb stuff that would otherwise be passed on directly to the carcass. A 2.35 Magic Mary Supergravityvertstar was also pretty good but had a lifetime measured in minutes.
If I had to choose I would go for a 2.4 3C wire bead Shorty. It’s the kind of tyre that stands up on it own and takes some of the load off the rims. On the back an HRII or an Onza DH 2.40 (the Onza is like a part-worn HR II) have both worked well for me
