Hi @████████, I will share with you a solution, but you need to readapt to your scenario. Because I build this in a Test form. 

If I understood your question correctly, I'll restate what the code I'm about to share below does:

I created a Radio Button with ID 1 (in your scenario you must change for the real one), and within the basic options, I checked the Assign Values ​​to Choices checkbox (this allowed me to be more specific when locating the value for the radio button). For this test, I set the following options:

Label: Choice 1, Value: Choice 1 * I didn't use this one; I just left it there as part of the example so you could observe the behavior of the other options.
Label: New Employee, Value: NE_Choice
Label: Employee Termination, Value: NE_Choice

You can see it better in this image if you have any questions:

Create a Checkbox with ID 2(you can change this for your real one). Just like I did with the Radio Button, I added some sample content:

Label: Choice 1, Value: Choice_1
Label: New User Account, Value: New_User_Account
Label: Employee Termination, Value: Employee_Termination

You can also see it in this image:

And then put this JavaScript Code in your JS Section: 

/*****************************************************************
 *  Radio Button (Field ID 1)                Checkbox (Field ID 2)
 *  ─────────────────────────────────────    ────────────────────────────────────
 *  Label                Value              Label                 Value
 *  ─────────────────────────────────────    ────────────────────────────────────
 *  New Employee         NE_Choice          New User Account      New_User_Account
 *  Employee Termination ET_Choice          Employee Termination  Employee_Termination
 *
 *  Behaviour:
 *    • Both checkbox options are hidden on load.
 *    • Selecting “New Employee”      → shows “New User Account”.
 *    • Selecting “Employee Termination” → shows “Employee Termination”.
 *****************************************************************/

const radioField    = { fieldId: 1 };
const checkboxField = { fieldId: 2 };

const checkboxOptions = {
  newAccount : { label: "New User Account",     value: "New_User_Account" },
  termination: { label: "Employee Termination", value: "Employee_Termination" }
};

/* -- Main sync function ----------------------------------------------------- */
async function syncCheckboxOptions() {
  /* 1 – Get current radio value (e.g. “NE_Choice”). */
  let radioValue = await LFForm.getFieldValues(radioField);
  if (radioValue && typeof radioValue === "object") radioValue = radioValue.value;

  /* 2 – Always remove both target options first. */
  await LFForm.changeFieldOptions(
    checkboxField,
    Object.values(checkboxOptions),
    "remove"
  );

  /* 3 – Decide which option (if any) to add back in. */
  let optionToAdd = null;
  if (radioValue === "NE_Choice") {
    optionToAdd = checkboxOptions.newAccount;
  } else if (radioValue === "ET_Choice") {
    optionToAdd = checkboxOptions.termination;
  }

  if (optionToAdd) {
    await LFForm.changeFieldOptions(checkboxField, [optionToAdd], "add");
  }

  /* 4 – Clear orphaned selections if the user had already checked something. */
  const current = await LFForm.getFieldValues(checkboxField);
  const allowed = optionToAdd ? [optionToAdd.value] : [];
  if (current?.value?.some(v => !allowed.includes(v))) {
    await LFForm.setFieldValues(checkboxField, { value: [] });
  }
}

/* Run once on load and again whenever the radio field changes. */
syncCheckboxOptions();
LFForm.onFieldChange(syncCheckboxOptions, radioField);

I hope this is what you're looking for. Let me know if it works for you.