I think the terms you're looking for are "choc spacing" and "MX spacing". Choc spacing is what the Piantor uses where the space for each key is 18 x 17 millimeters. MX spacing is 19 x 19 millimeters.

If you want to keep using low-profile switches, there are a handful of boards that either choc or MX switches, and any of those will always use MX spacing. That said, I don't think there are a lot of pre-built options in this space.

Maybe check out Klor. I think that one is offered as a pre-built by beekeeb and it uses MX switches. It's got the more aggressive pinky stagger, but it also has some splay which may or may not be your thing. I just finished building one using tecsee "medium" switches and MTNU keycaps, do it's lower profile, but still not as low as choc.

I'd try searching with the term pitch, as that is the typical term for an even spacing of an array of things.

"Key spacing" is usually the term.

I think Dao Choc BLE, city42, or the various Hillside keyboards would be the closest that you can get pre-built.

I had similar problems with a Cantor build, and I have pretty small hands. I think the problem was not necessarily the key spacing, but the flat key profile that makes it harder to feel the key positions and easier to press two keys at once. MX keys typically have larger gaps between the key tops, which makes orientation easier for me. Interestingly I also have no problem with chiclet keys on my laptop with 3mm gaps between keys.

I was hoping to try LDSA key caps to fix this, but they never came back in stock before I moved on from my Cantor. There are other sculpted key cap options to try. E.g. https://lowprokb.ca/collections/keycaps/products/ddc-choc-pbt-blank-keycaps, https://www.asymplex.xyz/product/cs-chicago-stenographer-profile or https://3dkeycap.com/products/klp-choc-keycap-set-low-profile-ergonomic-sculpted-keycaps.

It seems like most key spacing is pretty standard but if you used a board with mx switches, like the Corne, you'd have a bit more room.