Set the properties you need to override

/*
const options = {
view: {
height: () => document.documentElement.clientHeight - 41,
width: () => document.documentElement.clientWidth,
},
row: {
len: 100,
height: 25,
},
col: {
len: 26,
width: 100,
indexWidth: 60,
minWidth: 60,
},
style: {
bgcolor: '#ffffff',
align: 'left',
valign: 'middle',
textwrap: false,
textDecoration: 'normal',
strikethrough: false,
color: '#0a0a0a',
font: {
name: 'Helvetica',
size: 10,
bold: false,
italic: false,
},
},
}
*/
const options = {
  row: { len: 200 }
}
new Spreadsheet(el, options).loadData({});

Is there full documentation anywhere?

Can it handle 1M+ rows?

its OK In theory