How to create two text fields in single column in grid and make default selection of all rows in grid

Hi,

Please see the below code as an example for your requirements. I hope it will help... let me know if any concerns.

a!localVariables(
  local!condition: cons!ZMS_PEN_CONDITIONS,
  local!types: cons!ZMS_PEN_TYPES,
  a!formLayout(
    label: "Add Multiple Pens Data",
    contents: {
      a!gridLayout(
        totalCount: count(ri!items),
        headerCells: {
          a!gridLayoutHeaderCell(label: "Pen Name"),
          a!gridLayoutHeaderCell(label: "Type"),
          a!gridLayoutHeaderCell(label: "Condition"),
          a!gridLayoutHeaderCell(label: "Image"),
          a!gridLayoutHeaderCell(label: "Description"),
          /* For the "Remove" column */
          a!gridLayoutHeaderCell(label: "")
        },
        /* Only needed when some columns need to be narrow */
        columnConfigs: {
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 3),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 1),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 1),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 2),
          a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight: 3),
          a!gridLayoutColumnConfig(width: "ICON")
        },
        rows: a!forEach(
          items: ri!items,
          expression: a!gridRowLayout(
            id: fv!index,
            contents: {
              a!textField(
                label: "pen name " & fv!index,
                value: fv!item.penname,
                saveInto: fv!item.penname,
                required: true
              ),
              a!dropdownField(
                label: "condition " & fv!index,
                placeholder: "-- Select -- ",
                choiceLabels: local!types,
                choiceValues: local!types,
                value: fv!item.pentype,
                saveInto: fv!item.pentype,
                required: true
              ),
              a!dropdownField(
                label: "condition " & fv!index,
                placeholder: "-- Select -- ",
                choiceLabels: local!condition,
                choiceValues: local!condition,
                value: fv!item.pencondition,
                saveInto: fv!item.pencondition,
                required: true
              ),
              a!fileUploadField(
                target: cons!ZMS_PEN_IMAGE_FOLDER,
                maxSelections: 1,
                value: fv!item.penimage,
                saveInto: fv!item.penimage,
                required: true,
                requiredMessage: "pen image is required",
                validations: {
                  a!localVariables(
                    local!invalidExtensions: difference(
                      upper(fv!files.extension),
                      { "PNG", "JPG" }
                    ),
                    if(
                      length(local!invalidExtensions) > 0,
                      "Attachments must be images. Remove: " & index(
                        fv!files,
                        "name",
                        wherecontains(
                          local!invalidExtensions,
                          upper(fv!files.extension)
                        ),
                        {}
                      ),
                      ""
                    )
                  ),
                  if(
                    or(fv!files.size > 300000),
                    "Attachments may not exceed 300KB. Remove: " & index(
                      fv!files,
                      "name",
                      where(fv!files.size > 300000),
                      {}
                    ),
                    ""
                  )
                },
                buttonStyle: "SECONDARY",
                buttonSize: "STANDARD"
              ),
              a!textField(
                value: fv!item.characteristics,
                saveInto: fv!item.characteristics,
                characterLimit: 100,
                required: true,
                validationGroup: "main"
              ),
              /* For the Removal Column*/
              a!richTextDisplayField(
                value: a!richTextIcon(
                  icon: "close",
                  altText: "delete " & fv!index,
                  caption: "Remove " & fv!item.penname,
                  link: a!dynamicLink(
                    value: fv!index,
                    saveInto: {
                      a!save(ri!items, remove(ri!items, save!value))
                    }
                  ),
                  linkStyle: "STANDALONE",
                  color: "NEGATIVE"
                )
              )
            }
          )
        ),
        addRowlink: a!dynamicLink(
          label: "Add Pen",
          value: 'type!{urn:com:appian:types:ZMS}ZMS_Pens'(
            createdby: loggedInUser(),
            createddate: now(),
            status: "Active"
          ),
          saveInto: {
            a!save(ri!items, append(ri!items, save!value))
          }
        ),
        rowHeader: 1
      )
    },
    buttons: a!buttonLayout(
      primaryButtons: a!buttonWidget(
        label: "Submit",
        saveInto: a!writeToDataStoreEntity(
          dataStoreEntity: cons!ZMS_DSE_PENS,
          valueToStore: ri!items/*onSuccess: ri!items*/
          
        ),
        submit: true
      )
    )
  )
)

Please modify the code as per your fields.

Adding two components in a single cell is not possible. One cell can only have one component. 
I am assuming that you want all the rows to be selected NOT SELECTABLE by default. So for this, you need to pass the list of indexes of the rows the variable that is storing the selectionValue.